T
negative drag
- Thread starter [email protected]
- Start date
P
peter
Guest
On Dec 13, 7:02 pm, [email protected] wrote:
> On Thu, 13 Dec 2007 17:56:16 -0800 (PST), peter <[email protected]>
> wrote:
>
> [snip]
>
> >Now does this make any practical sense? No.
>
> [snip]
>
> Dear Peter,
>
> You're getting closer.
No, I'm continuing to say exactly what I did in my original post since
that was correct. Note that in that post I also indicated that the
effect would be too small to be practical and that a passive fairing
makes much more sense if the goal is to reduce the effects of wind
resistance.
>
> You can extract useful energy by sticking a propeller into an
> airstream to use onboard, just as you can extract useful energy
> through a generator's roller to run a light.
>
> You cannot, however, extract energy that is useful for propelling the
> vehicle forward _faster_ because you lose more than you gain.
The obvious difference here, as compared to turning on the generator,
is that no additional drag is created by placing the propeller into a
part of the airstream that would otherwise generate just as much drag
by hitting the cyclist directly. Look at the example I gave in the
previous post where the propeller is a slightly modified fairing shape
and may actually have less air resistance than the cyclist alone. In
that case there's a slight gain even if the energy extracted from the
wind is thrown away - and a slightly larger gain if it's used to aid
the propulsion of the cycle.
But, as I've said all along, I don't think the magnitude of the gain
in practice would be sufficient to justify the added weight,
bulkiness, and complex mechanism. Nevertheless, it is in no way a
perpetual motion machine (of either the first or second kinds) and
there is no physics principle that prohibits obtaining small
mechanical benefits by utilizing part of the wind energy that would
otherwise be wasted upon hitting the cyclist.
> On Thu, 13 Dec 2007 17:56:16 -0800 (PST), peter <[email protected]>
> wrote:
>
> [snip]
>
> >Now does this make any practical sense? No.
>
> [snip]
>
> Dear Peter,
>
> You're getting closer.
No, I'm continuing to say exactly what I did in my original post since
that was correct. Note that in that post I also indicated that the
effect would be too small to be practical and that a passive fairing
makes much more sense if the goal is to reduce the effects of wind
resistance.
>
> You can extract useful energy by sticking a propeller into an
> airstream to use onboard, just as you can extract useful energy
> through a generator's roller to run a light.
>
> You cannot, however, extract energy that is useful for propelling the
> vehicle forward _faster_ because you lose more than you gain.
The obvious difference here, as compared to turning on the generator,
is that no additional drag is created by placing the propeller into a
part of the airstream that would otherwise generate just as much drag
by hitting the cyclist directly. Look at the example I gave in the
previous post where the propeller is a slightly modified fairing shape
and may actually have less air resistance than the cyclist alone. In
that case there's a slight gain even if the energy extracted from the
wind is thrown away - and a slightly larger gain if it's used to aid
the propulsion of the cycle.
But, as I've said all along, I don't think the magnitude of the gain
in practice would be sufficient to justify the added weight,
bulkiness, and complex mechanism. Nevertheless, it is in no way a
perpetual motion machine (of either the first or second kinds) and
there is no physics principle that prohibits obtaining small
mechanical benefits by utilizing part of the wind energy that would
otherwise be wasted upon hitting the cyclist.
T
Tom Sherman
Guest
Tim McNamara wrote:
> "... and it has a fiberglass engine and it runs on water, man!"
What are you talking about?
--
Tom Sherman - Holstein-Friesland Bovinia
"Localized intense suction such as tornadoes is created when temperature
differences are high enough between meeting air masses, and can impart
excessive energy onto a cyclist." - Randy Schlitter
> "... and it has a fiberglass engine and it runs on water, man!"
What are you talking about?
--
Tom Sherman - Holstein-Friesland Bovinia
"Localized intense suction such as tornadoes is created when temperature
differences are high enough between meeting air masses, and can impart
excessive energy onto a cyclist." - Randy Schlitter
P
peter
Guest
On Dec 13, 8:18 pm, Tom Sherman <[email protected]>
wrote:
> Peter Rathman wrote:
> > ...
> > My car has a coefficient of drag of 0.35, and it has a much more
> > streamlined shape than a regular upright cyclist. Where did your
> > factor of 10 (implying a Cd of 0.1) come from? Figures I've seen for
> > normal cyclists have been more around 0.6 or 0.7....
>
> Here is what a bicycle with a coefficient of drag of slightly less than
> 0.1 looks like:
> <http://www.ent.ohiou.edu/~et181/hpv/Andrea_64.7mph.jpg>.
Agreed, and clearly for that kind of cycle adding any additional
external apparatus would add considerable extra drag since the shape
has already been optimized for minimum Cd. But the proposal in the
original post included illustrations that made it clear it was for a
regular upright cyclist - not even one in the drops or aero-bar
positions.
wrote:
> Peter Rathman wrote:
> > ...
> > My car has a coefficient of drag of 0.35, and it has a much more
> > streamlined shape than a regular upright cyclist. Where did your
> > factor of 10 (implying a Cd of 0.1) come from? Figures I've seen for
> > normal cyclists have been more around 0.6 or 0.7....
>
> Here is what a bicycle with a coefficient of drag of slightly less than
> 0.1 looks like:
> <http://www.ent.ohiou.edu/~et181/hpv/Andrea_64.7mph.jpg>.
Agreed, and clearly for that kind of cycle adding any additional
external apparatus would add considerable extra drag since the shape
has already been optimized for minimum Cd. But the proposal in the
original post included illustrations that made it clear it was for a
regular upright cyclist - not even one in the drops or aero-bar
positions.
U
On Dec 13, 8:56 pm, peter <[email protected]> wrote:
> For example, the object we put out in front of the cyclist could be in
> the shape of an aerodynamic nose cone. Let's say a fairing of that
> type cuts his wind resistance by 20%. Now we add some bearings and
> little fins to the nose cone so it'll start rotating in the wind. The
> fins will obviously add back some air resistance, but by keeping them
> small we can make sure that the overall result is still no worse than
> the unfaired cyclist. Any energy we can extract from the spinning
> cone and use for propulsion is now a net plus if we're only interested
> in power needed to overcome air resistance.
No. Starting with your initial nose cone, the cyclist is putting a
certain amount of power into the system. Once you add the fins, you
start transferring additional momentum from the air into spinning the
fairing. Recall that aerodynamic drag is a vector quantity, not a
scalar. Adding rotational drag to a body will not decrease drag in
the axial direction. In order for this additional rotation to
decrease the total power requirement from the cyclist, more power
needs to be extracted from the rotating fairing than is put into it.
This is simply not possible.
> For example, the object we put out in front of the cyclist could be in
> the shape of an aerodynamic nose cone. Let's say a fairing of that
> type cuts his wind resistance by 20%. Now we add some bearings and
> little fins to the nose cone so it'll start rotating in the wind. The
> fins will obviously add back some air resistance, but by keeping them
> small we can make sure that the overall result is still no worse than
> the unfaired cyclist. Any energy we can extract from the spinning
> cone and use for propulsion is now a net plus if we're only interested
> in power needed to overcome air resistance.
No. Starting with your initial nose cone, the cyclist is putting a
certain amount of power into the system. Once you add the fins, you
start transferring additional momentum from the air into spinning the
fairing. Recall that aerodynamic drag is a vector quantity, not a
scalar. Adding rotational drag to a body will not decrease drag in
the axial direction. In order for this additional rotation to
decrease the total power requirement from the cyclist, more power
needs to be extracted from the rotating fairing than is put into it.
This is simply not possible.
U
On Dec 13, 10:21 pm, "[email protected]" <[email protected]> wrote:
> On Dec 14, 2:49 am, "Leo Lichtman" <[email protected]>
> wrote:
>
> > I sat down and designed a propeller that would increase the speed of a
> > bicycle with NO INCREASE IN POWER INPUT. I wound up with a propeller that
> > had no moving parts, and whose blades were shaped like a fairing.
>
> Me to.
>
> A slight spiral shape should generate centrifugal force depending on
> the speed and drag. Then have a recumbent slide down the vacuum in the
> center of a vortex. It's that what Victor Schauberger calls light air.
>
> But to smoothly pedal the air up to speed the bike would become much
> to long.
>
> That's why one would use a propeller I think. Or a rotating cone.
>
> I doubt efficiently gearing windmills to the wheels a bit.
>
> It would be better to use the wind to further enhance the air flow.
>
> http://gabydewilde.googlepages.com/negative-drag
> gabydewilde - negative drag
But where is this magical vortex coming from? Generating a vortex
from an axial flow consumes so much energy that the aeronautics
industry has spent decades developing wing tips specifically not to
create them. There are some very good fundamental reasons why
mainstream aerodynamic vehicle design has been focused on transferring
the minimum possible amount of momentum to the air. If your own study
of fluid dynamics had extended past reading crackpot theories on the
internet, it might be more clear to you.
> On Dec 14, 2:49 am, "Leo Lichtman" <[email protected]>
> wrote:
>
> > I sat down and designed a propeller that would increase the speed of a
> > bicycle with NO INCREASE IN POWER INPUT. I wound up with a propeller that
> > had no moving parts, and whose blades were shaped like a fairing.
>
> Me to.
>
> A slight spiral shape should generate centrifugal force depending on
> the speed and drag. Then have a recumbent slide down the vacuum in the
> center of a vortex. It's that what Victor Schauberger calls light air.
>
> But to smoothly pedal the air up to speed the bike would become much
> to long.
>
> That's why one would use a propeller I think. Or a rotating cone.
>
> I doubt efficiently gearing windmills to the wheels a bit.
>
> It would be better to use the wind to further enhance the air flow.
>
> http://gabydewilde.googlepages.com/negative-drag
> gabydewilde - negative drag
But where is this magical vortex coming from? Generating a vortex
from an axial flow consumes so much energy that the aeronautics
industry has spent decades developing wing tips specifically not to
create them. There are some very good fundamental reasons why
mainstream aerodynamic vehicle design has been focused on transferring
the minimum possible amount of momentum to the air. If your own study
of fluid dynamics had extended past reading crackpot theories on the
internet, it might be more clear to you.
A
Androcles
Guest
<[email protected]> wrote in message
news:bc73b6a8-49a9-46ba-be64-5185205c15b8@s19g2000prg.googlegroups.com...
: On Dec 13, 10:21 pm, "[email protected]" <[email protected]> wrote:
: > On Dec 14, 2:49 am, "Leo Lichtman" <[email protected]>
: > wrote:
: >
: > > I sat down and designed a propeller that would increase the speed of a
: > > bicycle with NO INCREASE IN POWER INPUT. I wound up with a propeller
that
: > > had no moving parts, and whose blades were shaped like a fairing.
: >
: > Me to.
I sat down and designed a bicycle with no propeller.
I wound up with pedals that increased the speed by
pushing on them.
news:bc73b6a8-49a9-46ba-be64-5185205c15b8@s19g2000prg.googlegroups.com...
: On Dec 13, 10:21 pm, "[email protected]" <[email protected]> wrote:
: > On Dec 14, 2:49 am, "Leo Lichtman" <[email protected]>
: > wrote:
: >
: > > I sat down and designed a propeller that would increase the speed of a
: > > bicycle with NO INCREASE IN POWER INPUT. I wound up with a propeller
that
: > > had no moving parts, and whose blades were shaped like a fairing.
: >
: > Me to.
I sat down and designed a bicycle with no propeller.
I wound up with pedals that increased the speed by
pushing on them.
U
On Dec 14, 12:35 am, Tom Sherman <[email protected]>
wrote:
> Tim McNamara wrote:
> > "... and it has a fiberglass engine and it runs on water, man!"
>
> What are you talking about?
>
> --
> Tom Sherman - Holstein-Friesland Bovinia
> "Localized intense suction such as tornadoes is created when temperature
> differences are high enough between meeting air masses, and can impart
> excessive energy onto a cyclist." - Randy Schlitter
I believe he's suggesting that our friend Gaby might be developing her
theories with some kind of herbal assistance.
wrote:
> Tim McNamara wrote:
> > "... and it has a fiberglass engine and it runs on water, man!"
>
> What are you talking about?
>
> --
> Tom Sherman - Holstein-Friesland Bovinia
> "Localized intense suction such as tornadoes is created when temperature
> differences are high enough between meeting air masses, and can impart
> excessive energy onto a cyclist." - Randy Schlitter
I believe he's suggesting that our friend Gaby might be developing her
theories with some kind of herbal assistance.
P
peter
Guest
On Dec 14, 5:55 am, [email protected] wrote:
> On Dec 13, 8:56 pm, peter <[email protected]> wrote:
>
> > For example, the object we put out in front of the cyclist could be in
> > the shape of an aerodynamic nose cone. Let's say a fairing of that
> > type cuts his wind resistance by 20%. Now we add some bearings and
> > little fins to the nose cone so it'll start rotating in the wind. The
> > fins will obviously add back some air resistance, but by keeping them
> > small we can make sure that the overall result is still no worse than
> > the unfaired cyclist. Any energy we can extract from the spinning
> > cone and use for propulsion is now a net plus if we're only interested
> > in power needed to overcome air resistance.
>
> No. Starting with your initial nose cone, the cyclist is putting a
> certain amount of power into the system.
But we're *not* starting with an initial nose cone - we're starting
with a regular upright cyclist. We're then adding a reasonably
aerodynamic windmill right in front of him that consists of a nose
cone shape with fins along the side so it spins when in the wind. The
combination of original rider/bike plus the added windmill can be made
to have the same, or even slightly less, air resistance than the rider/
bike had. Therefore adding the windmill didn't add any extra drag.
But it does allow you to extract some small amount of power from the
wind - power that was wasted before in creating extra turbulence as
the wind hit the decidedly non-aerodynamic rider. Not enough to be at
all practical, but enough to show that in principle some energy can be
extracted.
Note that I had already explicitly said before that the windmill is
not as aerodynamic as the plain unfinned nose cone - but that's not
the comparison since we never actually have the unfinned nose cone.
We start with the plain rider/bike and we add the finned nose cone as
the windmill element.
> Once you add the fins, you
> start transferring additional momentum from the air into spinning the
> fairing. Recall that aerodynamic drag is a vector quantity, not a
> scalar. Adding rotational drag to a body will not decrease drag in
> the axial direction. In order for this additional rotation to
> decrease the total power requirement from the cyclist, more power
> needs to be extracted from the rotating fairing than is put into it.
> This is simply not possible.
> On Dec 13, 8:56 pm, peter <[email protected]> wrote:
>
> > For example, the object we put out in front of the cyclist could be in
> > the shape of an aerodynamic nose cone. Let's say a fairing of that
> > type cuts his wind resistance by 20%. Now we add some bearings and
> > little fins to the nose cone so it'll start rotating in the wind. The
> > fins will obviously add back some air resistance, but by keeping them
> > small we can make sure that the overall result is still no worse than
> > the unfaired cyclist. Any energy we can extract from the spinning
> > cone and use for propulsion is now a net plus if we're only interested
> > in power needed to overcome air resistance.
>
> No. Starting with your initial nose cone, the cyclist is putting a
> certain amount of power into the system.
But we're *not* starting with an initial nose cone - we're starting
with a regular upright cyclist. We're then adding a reasonably
aerodynamic windmill right in front of him that consists of a nose
cone shape with fins along the side so it spins when in the wind. The
combination of original rider/bike plus the added windmill can be made
to have the same, or even slightly less, air resistance than the rider/
bike had. Therefore adding the windmill didn't add any extra drag.
But it does allow you to extract some small amount of power from the
wind - power that was wasted before in creating extra turbulence as
the wind hit the decidedly non-aerodynamic rider. Not enough to be at
all practical, but enough to show that in principle some energy can be
extracted.
Note that I had already explicitly said before that the windmill is
not as aerodynamic as the plain unfinned nose cone - but that's not
the comparison since we never actually have the unfinned nose cone.
We start with the plain rider/bike and we add the finned nose cone as
the windmill element.
> Once you add the fins, you
> start transferring additional momentum from the air into spinning the
> fairing. Recall that aerodynamic drag is a vector quantity, not a
> scalar. Adding rotational drag to a body will not decrease drag in
> the axial direction. In order for this additional rotation to
> decrease the total power requirement from the cyclist, more power
> needs to be extracted from the rotating fairing than is put into it.
> This is simply not possible.
U
On Dec 14, 11:01 am, peter <[email protected]> wrote:
> On Dec 14, 5:55 am, [email protected] wrote:
>
> > On Dec 13, 8:56 pm, peter <[email protected]> wrote:
>
> > > For example, the object we put out in front of the cyclist could be in
> > > the shape of an aerodynamic nose cone. Let's say a fairing of that
> > > type cuts his wind resistance by 20%. Now we add some bearings and
> > > little fins to the nose cone so it'll start rotating in the wind. The
> > > fins will obviously add back some air resistance, but by keeping them
> > > small we can make sure that the overall result is still no worse than
> > > the unfaired cyclist. Any energy we can extract from the spinning
> > > cone and use for propulsion is now a net plus if we're only interested
> > > in power needed to overcome air resistance.
>
> > No. Starting with your initial nose cone, the cyclist is putting a
> > certain amount of power into the system.
>
> But we're *not* starting with an initial nose cone - we're starting
> with a regular upright cyclist. We're then adding a reasonably
> aerodynamic windmill right in front of him that consists of a nose
> cone shape with fins along the side so it spins when in the wind. The
> combination of original rider/bike plus the added windmill can be made
> to have the same, or even slightly less, air resistance than the rider/
> bike had. Therefore adding the windmill didn't add any extra drag.
> But it does allow you to extract some small amount of power from the
> wind - power that was wasted before in creating extra turbulence as
> the wind hit the decidedly non-aerodynamic rider. Not enough to be at
> all practical, but enough to show that in principle some energy can be
> extracted.
>
> Note that I had already explicitly said before that the windmill is
> not as aerodynamic as the plain unfinned nose cone - but that's not
> the comparison since we never actually have the unfinned nose cone.
> We start with the plain rider/bike and we add the finned nose cone as
> the windmill element.
>
> > Once you add the fins, you
> > start transferring additional momentum from the air into spinning the
> > fairing. Recall that aerodynamic drag is a vector quantity, not a
> > scalar. Adding rotational drag to a body will not decrease drag in
> > the axial direction. In order for this additional rotation to
> > decrease the total power requirement from the cyclist, more power
> > needs to be extracted from the rotating fairing than is put into it.
> > This is simply not possible.
You can't suggest a nose cone, and then say it was never there. Sure,
some finned, spinning, nose cone contraption might be more areodynamic
than the cyclist alone, but it's physically impossible for it the
system to be as efficient as the un-finned, non-spinning fairing. So
why make it spin and try to get the energy back out that you put into
it to make it spin in the first place?
> On Dec 14, 5:55 am, [email protected] wrote:
>
> > On Dec 13, 8:56 pm, peter <[email protected]> wrote:
>
> > > For example, the object we put out in front of the cyclist could be in
> > > the shape of an aerodynamic nose cone. Let's say a fairing of that
> > > type cuts his wind resistance by 20%. Now we add some bearings and
> > > little fins to the nose cone so it'll start rotating in the wind. The
> > > fins will obviously add back some air resistance, but by keeping them
> > > small we can make sure that the overall result is still no worse than
> > > the unfaired cyclist. Any energy we can extract from the spinning
> > > cone and use for propulsion is now a net plus if we're only interested
> > > in power needed to overcome air resistance.
>
> > No. Starting with your initial nose cone, the cyclist is putting a
> > certain amount of power into the system.
>
> But we're *not* starting with an initial nose cone - we're starting
> with a regular upright cyclist. We're then adding a reasonably
> aerodynamic windmill right in front of him that consists of a nose
> cone shape with fins along the side so it spins when in the wind. The
> combination of original rider/bike plus the added windmill can be made
> to have the same, or even slightly less, air resistance than the rider/
> bike had. Therefore adding the windmill didn't add any extra drag.
> But it does allow you to extract some small amount of power from the
> wind - power that was wasted before in creating extra turbulence as
> the wind hit the decidedly non-aerodynamic rider. Not enough to be at
> all practical, but enough to show that in principle some energy can be
> extracted.
>
> Note that I had already explicitly said before that the windmill is
> not as aerodynamic as the plain unfinned nose cone - but that's not
> the comparison since we never actually have the unfinned nose cone.
> We start with the plain rider/bike and we add the finned nose cone as
> the windmill element.
>
> > Once you add the fins, you
> > start transferring additional momentum from the air into spinning the
> > fairing. Recall that aerodynamic drag is a vector quantity, not a
> > scalar. Adding rotational drag to a body will not decrease drag in
> > the axial direction. In order for this additional rotation to
> > decrease the total power requirement from the cyclist, more power
> > needs to be extracted from the rotating fairing than is put into it.
> > This is simply not possible.
You can't suggest a nose cone, and then say it was never there. Sure,
some finned, spinning, nose cone contraption might be more areodynamic
than the cyclist alone, but it's physically impossible for it the
system to be as efficient as the un-finned, non-spinning fairing. So
why make it spin and try to get the energy back out that you put into
it to make it spin in the first place?
D
datakoll
Guest
a reasonably aerodynamic windmill?
that's the point where creative writing enters from, well, use the
lift-stage center.
like magic tricks, right? gues which shell hides the pea? say look
over there at the naked cheerleader.. why there's the pea under shell
one.
distract the reader then write "reasonably aerodynamic windmill cited
by Pieere La Fountainblue, Academy la Marseille Vol 36 Letters
that's the point where creative writing enters from, well, use the
lift-stage center.
like magic tricks, right? gues which shell hides the pea? say look
over there at the naked cheerleader.. why there's the pea under shell
one.
distract the reader then write "reasonably aerodynamic windmill cited
by Pieere La Fountainblue, Academy la Marseille Vol 36 Letters
G
On Dec 14, 5:40 pm, [email protected] wrote:
> You can't suggest a nose cone, and then say it was never there. Sure,
> some finned, spinning, nose cone contraption might be more areodynamic
> than the cyclist alone, but it's physically impossible for it the
> system to be as efficient as the un-finned, non-spinning fairing.
I can accept a closed body being more efficient as just a propeller.
Still you are arguing about using only the drag. Sailing does not work
like that.
Here you have a picture again. I think you missed it before.
http://i.treehugger.com/images/2007-2-21/Windmill-Sailboat.jpg
The faster you go the more the wind turns into your face so one might
as well put the propeller at the front.
This is why it must spin.
> So
> why make it spin and try to get the energy back out that you put into
> it to make it spin in the first place?
I'm hoping the wind can buy us a sucking vortex.
I've made a new thread for the vortex cone here.
http://groups.google.com/group/rec.bicycles.tech/browse_frm/thread/921e418d6cffd70d
More rotary "excuses".
Enjoy.
> You can't suggest a nose cone, and then say it was never there. Sure,
> some finned, spinning, nose cone contraption might be more areodynamic
> than the cyclist alone, but it's physically impossible for it the
> system to be as efficient as the un-finned, non-spinning fairing.
I can accept a closed body being more efficient as just a propeller.
Still you are arguing about using only the drag. Sailing does not work
like that.
Here you have a picture again. I think you missed it before.
http://i.treehugger.com/images/2007-2-21/Windmill-Sailboat.jpg
The faster you go the more the wind turns into your face so one might
as well put the propeller at the front.
This is why it must spin.
> So
> why make it spin and try to get the energy back out that you put into
> it to make it spin in the first place?
I'm hoping the wind can buy us a sucking vortex.
I've made a new thread for the vortex cone here.
http://groups.google.com/group/rec.bicycles.tech/browse_frm/thread/921e418d6cffd70d
More rotary "excuses".
Enjoy.
T
Tom Sherman
Guest
[email protected] who? wrote:
> On Dec 14, 11:01 am, peter <[email protected]> wrote:
>> On Dec 14, 5:55 am, [email protected] wrote:
>>
>>> On Dec 13, 8:56 pm, peter <[email protected]> wrote:
>>>> For example, the object we put out in front of the cyclist could be in
>>>> the shape of an aerodynamic nose cone. Let's say a fairing of that
>>>> type cuts his wind resistance by 20%. Now we add some bearings and
>>>> little fins to the nose cone so it'll start rotating in the wind. The
>>>> fins will obviously add back some air resistance, but by keeping them
>>>> small we can make sure that the overall result is still no worse than
>>>> the unfaired cyclist. Any energy we can extract from the spinning
>>>> cone and use for propulsion is now a net plus if we're only interested
>>>> in power needed to overcome air resistance.
>>> No. Starting with your initial nose cone, the cyclist is putting a
>>> certain amount of power into the system.
>> But we're *not* starting with an initial nose cone - we're starting
>> with a regular upright cyclist. We're then adding a reasonably
>> aerodynamic windmill right in front of him that consists of a nose
>> cone shape with fins along the side so it spins when in the wind. The
>> combination of original rider/bike plus the added windmill can be made
>> to have the same, or even slightly less, air resistance than the rider/
>> bike had. Therefore adding the windmill didn't add any extra drag.
>> But it does allow you to extract some small amount of power from the
>> wind - power that was wasted before in creating extra turbulence as
>> the wind hit the decidedly non-aerodynamic rider. Not enough to be at
>> all practical, but enough to show that in principle some energy can be
>> extracted.
>>
>> Note that I had already explicitly said before that the windmill is
>> not as aerodynamic as the plain unfinned nose cone - but that's not
>> the comparison since we never actually have the unfinned nose cone.
>> We start with the plain rider/bike and we add the finned nose cone as
>> the windmill element.
>>
>>> Once you add the fins, you
>>> start transferring additional momentum from the air into spinning the
>>> fairing. Recall that aerodynamic drag is a vector quantity, not a
>>> scalar. Adding rotational drag to a body will not decrease drag in
>>> the axial direction. In order for this additional rotation to
>>> decrease the total power requirement from the cyclist, more power
>>> needs to be extracted from the rotating fairing than is put into it.
>>> This is simply not possible.
>
> You can't suggest a nose cone, and then say it was never there. Sure,
> some finned, spinning, nose cone contraption might be more areodynamic
> than the cyclist alone, but it's physically impossible for it the
> system to be as efficient as the un-finned, non-spinning fairing. So
> why make it spin and try to get the energy back out that you put into
> it to make it spin in the first place?
With the proper lighting, a spinning nose cone would look really cool at
night.
--
Tom Sherman - Holstein-Friesland Bovinia
"Localized intense suction such as tornadoes is created when temperature
differences are high enough between meeting air masses, and can impart
excessive energy onto a cyclist." - Randy Schlitter
> On Dec 14, 11:01 am, peter <[email protected]> wrote:
>> On Dec 14, 5:55 am, [email protected] wrote:
>>
>>> On Dec 13, 8:56 pm, peter <[email protected]> wrote:
>>>> For example, the object we put out in front of the cyclist could be in
>>>> the shape of an aerodynamic nose cone. Let's say a fairing of that
>>>> type cuts his wind resistance by 20%. Now we add some bearings and
>>>> little fins to the nose cone so it'll start rotating in the wind. The
>>>> fins will obviously add back some air resistance, but by keeping them
>>>> small we can make sure that the overall result is still no worse than
>>>> the unfaired cyclist. Any energy we can extract from the spinning
>>>> cone and use for propulsion is now a net plus if we're only interested
>>>> in power needed to overcome air resistance.
>>> No. Starting with your initial nose cone, the cyclist is putting a
>>> certain amount of power into the system.
>> But we're *not* starting with an initial nose cone - we're starting
>> with a regular upright cyclist. We're then adding a reasonably
>> aerodynamic windmill right in front of him that consists of a nose
>> cone shape with fins along the side so it spins when in the wind. The
>> combination of original rider/bike plus the added windmill can be made
>> to have the same, or even slightly less, air resistance than the rider/
>> bike had. Therefore adding the windmill didn't add any extra drag.
>> But it does allow you to extract some small amount of power from the
>> wind - power that was wasted before in creating extra turbulence as
>> the wind hit the decidedly non-aerodynamic rider. Not enough to be at
>> all practical, but enough to show that in principle some energy can be
>> extracted.
>>
>> Note that I had already explicitly said before that the windmill is
>> not as aerodynamic as the plain unfinned nose cone - but that's not
>> the comparison since we never actually have the unfinned nose cone.
>> We start with the plain rider/bike and we add the finned nose cone as
>> the windmill element.
>>
>>> Once you add the fins, you
>>> start transferring additional momentum from the air into spinning the
>>> fairing. Recall that aerodynamic drag is a vector quantity, not a
>>> scalar. Adding rotational drag to a body will not decrease drag in
>>> the axial direction. In order for this additional rotation to
>>> decrease the total power requirement from the cyclist, more power
>>> needs to be extracted from the rotating fairing than is put into it.
>>> This is simply not possible.
>
> You can't suggest a nose cone, and then say it was never there. Sure,
> some finned, spinning, nose cone contraption might be more areodynamic
> than the cyclist alone, but it's physically impossible for it the
> system to be as efficient as the un-finned, non-spinning fairing. So
> why make it spin and try to get the energy back out that you put into
> it to make it spin in the first place?
With the proper lighting, a spinning nose cone would look really cool at
night.
--
Tom Sherman - Holstein-Friesland Bovinia
"Localized intense suction such as tornadoes is created when temperature
differences are high enough between meeting air masses, and can impart
excessive energy onto a cyclist." - Randy Schlitter
G
On Dec 15, 3:49 am, Tom Sherman <[email protected]>
wrote:
> [email protected] who? wrote:
> > On Dec 14, 11:01 am, peter <[email protected]> wrote:
> >> On Dec 14, 5:55 am, [email protected] wrote:
>
> >>> On Dec 13, 8:56 pm, peter <[email protected]> wrote:
> >>>> For example, the object we put out in front of the cyclist could be in
> >>>> the shape of an aerodynamic nose cone. Let's say a fairing of that
> >>>> type cuts his wind resistance by 20%. Now we add some bearings and
> >>>> little fins to the nose cone so it'll start rotating in the wind. The
> >>>> fins will obviously add back some air resistance, but by keeping them
> >>>> small we can make sure that the overall result is still no worse than
> >>>> the unfaired cyclist. Any energy we can extract from the spinning
> >>>> cone and use for propulsion is now a net plus if we're only interested
> >>>> in power needed to overcome air resistance.
> >>> No. Starting with your initial nose cone, the cyclist is putting a
> >>> certain amount of power into the system.
> >> But we're *not* starting with an initial nose cone - we're starting
> >> with a regular upright cyclist. We're then adding a reasonably
> >> aerodynamic windmill right in front of him that consists of a nose
> >> cone shape with fins along the side so it spins when in the wind. The
> >> combination of original rider/bike plus the added windmill can be made
> >> to have the same, or even slightly less, air resistance than the rider/
> >> bike had. Therefore adding the windmill didn't add any extra drag.
> >> But it does allow you to extract some small amount of power from the
> >> wind - power that was wasted before in creating extra turbulence as
> >> the wind hit the decidedly non-aerodynamic rider. Not enough to be at
> >> all practical, but enough to show that in principle some energy can be
> >> extracted.
>
> >> Note that I had already explicitly said before that the windmill is
> >> not as aerodynamic as the plain unfinned nose cone - but that's not
> >> the comparison since we never actually have the unfinned nose cone.
> >> We start with the plain rider/bike and we add the finned nose cone as
> >> the windmill element.
>
> >>> Once you add the fins, you
> >>> start transferring additional momentum from the air into spinning the
> >>> fairing. Recall that aerodynamic drag is a vector quantity, not a
> >>> scalar. Adding rotational drag to a body will not decrease drag in
> >>> the axial direction. In order for this additional rotation to
> >>> decrease the total power requirement from the cyclist, more power
> >>> needs to be extracted from the rotating fairing than is put into it.
> >>> This is simply not possible.
>
> > You can't suggest a nose cone, and then say it was never there. Sure,
> > some finned, spinning, nose cone contraption might be more areodynamic
> > than the cyclist alone, but it's physically impossible for it the
> > system to be as efficient as the un-finned, non-spinning fairing. So
> > why make it spin and try to get the energy back out that you put into
> > it to make it spin in the first place?
>
> With the proper lighting, a spinning nose cone would look really cool at
> night.
>
You get extra points for this Tom.
lol
wrote:
> [email protected] who? wrote:
> > On Dec 14, 11:01 am, peter <[email protected]> wrote:
> >> On Dec 14, 5:55 am, [email protected] wrote:
>
> >>> On Dec 13, 8:56 pm, peter <[email protected]> wrote:
> >>>> For example, the object we put out in front of the cyclist could be in
> >>>> the shape of an aerodynamic nose cone. Let's say a fairing of that
> >>>> type cuts his wind resistance by 20%. Now we add some bearings and
> >>>> little fins to the nose cone so it'll start rotating in the wind. The
> >>>> fins will obviously add back some air resistance, but by keeping them
> >>>> small we can make sure that the overall result is still no worse than
> >>>> the unfaired cyclist. Any energy we can extract from the spinning
> >>>> cone and use for propulsion is now a net plus if we're only interested
> >>>> in power needed to overcome air resistance.
> >>> No. Starting with your initial nose cone, the cyclist is putting a
> >>> certain amount of power into the system.
> >> But we're *not* starting with an initial nose cone - we're starting
> >> with a regular upright cyclist. We're then adding a reasonably
> >> aerodynamic windmill right in front of him that consists of a nose
> >> cone shape with fins along the side so it spins when in the wind. The
> >> combination of original rider/bike plus the added windmill can be made
> >> to have the same, or even slightly less, air resistance than the rider/
> >> bike had. Therefore adding the windmill didn't add any extra drag.
> >> But it does allow you to extract some small amount of power from the
> >> wind - power that was wasted before in creating extra turbulence as
> >> the wind hit the decidedly non-aerodynamic rider. Not enough to be at
> >> all practical, but enough to show that in principle some energy can be
> >> extracted.
>
> >> Note that I had already explicitly said before that the windmill is
> >> not as aerodynamic as the plain unfinned nose cone - but that's not
> >> the comparison since we never actually have the unfinned nose cone.
> >> We start with the plain rider/bike and we add the finned nose cone as
> >> the windmill element.
>
> >>> Once you add the fins, you
> >>> start transferring additional momentum from the air into spinning the
> >>> fairing. Recall that aerodynamic drag is a vector quantity, not a
> >>> scalar. Adding rotational drag to a body will not decrease drag in
> >>> the axial direction. In order for this additional rotation to
> >>> decrease the total power requirement from the cyclist, more power
> >>> needs to be extracted from the rotating fairing than is put into it.
> >>> This is simply not possible.
>
> > You can't suggest a nose cone, and then say it was never there. Sure,
> > some finned, spinning, nose cone contraption might be more areodynamic
> > than the cyclist alone, but it's physically impossible for it the
> > system to be as efficient as the un-finned, non-spinning fairing. So
> > why make it spin and try to get the energy back out that you put into
> > it to make it spin in the first place?
>
> With the proper lighting, a spinning nose cone would look really cool at
> night.
>
You get extra points for this Tom.
lol
C
CWatters
Guest
"Vince Morgan" <vinharAtHereoptusnet.com.au> wrote in message
news:[email protected]...
>
> "CWatters" <[email protected]> wrote in message
> news:[email protected]...
> >
> > "Elmo" <[email protected]> wrote in message
> > news:[email protected]...
> > > Of course what would really happen is that the wind would initially
> blow
> > > you backwards slightly, the backwards motion causing the fan to rotate
> > > backwards which would cause you to go backwards faster, causing the
fan
> > > to rotate faster and so on. The effect would snowball until you were
> > > going backwards at the speed of sound.
> > >
> > > elmo
> >
> > One of these can sail dead into wind....
> >
> > http://i.treehugger.com/images/2007-2-21/Windmill-Sailboat.jpg
> >
> It can? How is that possible?
> Vince
>
Why is it impossible? What physical laws does it break?
A sailing boat can tack upwind. There is little difference. Think about two
sailing boats on opposite tacks towing the same barge. The sail boats go
back and forth but the barge can be towed directly up wind. Look down on a
windmill from above and you see one blade going left to right and the other
right to left.
I believe there was a you tube clip somewhere on the web once.
More examples and some discussion..
http://www.boatdesign.net/forums/showthread.php?t=14182
news:[email protected]...
>
> "CWatters" <[email protected]> wrote in message
> news:[email protected]...
> >
> > "Elmo" <[email protected]> wrote in message
> > news:[email protected]...
> > > Of course what would really happen is that the wind would initially
> blow
> > > you backwards slightly, the backwards motion causing the fan to rotate
> > > backwards which would cause you to go backwards faster, causing the
fan
> > > to rotate faster and so on. The effect would snowball until you were
> > > going backwards at the speed of sound.
> > >
> > > elmo
> >
> > One of these can sail dead into wind....
> >
> > http://i.treehugger.com/images/2007-2-21/Windmill-Sailboat.jpg
> >
> It can? How is that possible?
> Vince
>
Why is it impossible? What physical laws does it break?
A sailing boat can tack upwind. There is little difference. Think about two
sailing boats on opposite tacks towing the same barge. The sail boats go
back and forth but the barge can be towed directly up wind. Look down on a
windmill from above and you see one blade going left to right and the other
right to left.
I believe there was a you tube clip somewhere on the web once.
More examples and some discussion..
http://www.boatdesign.net/forums/showthread.php?t=14182
G
On Dec 15, 3:47 pm, "CWatters" <[email protected]>
wrote:
> "Vince Morgan" <vinharAtHereoptusnet.com.au> wrote in message
> news:[email protected]...
> > "CWatters" <[email protected]> wrote in message
> >news:[email protected]...
> > > "Elmo" <[email protected]> wrote in message
> > >news:[email protected]...
> > > > Of course what would really happen is that the wind would initially
> > blow
> > > > you backwards slightly, the backwards motion causing the fan to rotate
> > > > backwards which would cause you to go backwards faster, causing the
> fan
> > > > to rotate faster and so on. The effect would snowball until you were
> > > > going backwards at the speed of sound.
>
> > > > elmo
>
> > > One of these can sail dead into wind....
>
> > >http://i.treehugger.com/images/2007-2-21/Windmill-Sailboat.jpg
>
> > It can? How is that possible?
> > Vince
>
> Why is it impossible? What physical laws does it break?
>
> A sailing boat can tack upwind. There is little difference. Think about two
> sailing boats on opposite tacks towing the same barge. The sail boats go
> back and forth but the barge can be towed directly up wind. Look down on a
> windmill from above and you see one blade going left to right and the other
> right to left.
>
> I believe there was a you tube clip somewhere on the web once.
>
> More examples and some discussion..http://www.boatdesign.net/forums/showthread.php?t=14182
Hey hello,
That's a great topic Colin. There is so much to learn here. I bet you
will be crying from laughter when you figure out this negative drag
topic.
I mean, almost everyone else is looking for excuses not to look? And
not looking equals not knowing. No matter how often one self proclaims
being an expert. At best they are experts at finding excuses not to
investigate things.
Down the wind the vehicle has contact with 2 mediums. We should
picture the vehicle as traveling inside the wind using the relatively
moving road as it's propulsion to be able to move down the wind
faster. Or move relative to the medium it sits in.
A poster in the topic above suggest the combination of going faster as
the wind and going directly up the wind. Apparently there are even a
lot of fly-cycles today. I've seen so much propeller driven crafts by
now I'm starting to think it would not require any extra parts to do a
little bit of both. One could both go twice as fast as the wind and
sail straight up the wind using the same rig.
I have a good idea how this guy's special windmill works.
http://www.sailwings.net
Peter Worsley - Wingsailing
http://www.sailwings.net/markone.html
Peter Worsley - Wingsailing Mark 1
http://www.sailwings.net/marktwo.html
Peter Worsley - Wingsailing
http://www.sailwings.net/tldescribed.html
Peter Worsley - Wingsailing
http://www.sailwings.net/wingelec.html
Peter Worsley - Wingsail/Electric
http://www.sailwings.net/article.html
Peter Worsley - Wingsailing
Nice stuff he has.
As a hint all I needed was to know we missed something rather foolish
while deploying the windmill in our imaginations.
But.......
....... if you can sail 45 degrees up the wind faster as you can sail
down it. Then why would we put the windmill straight up the wind! The
thing can stand under an angle and tack the blade up wind half a
rotation then have it capture the full wind over the other half. The
wind is still coming from straight ahead but it's pushing against the
side of the boat now!
This is how the blades stand while sailing up the wind.
http://i.treehugger.com/images/2007-2-21/Windmill-Sailboat.jpg
It's not facing forwards as that would subtract the wind force from
the kinetic energy.
I had already half figured this out with the vortex recumbent cone.
http://gabydewilde.googlepages.com/vortex-recumbent
gabydewilde - vortex recumbent
use side wind rather then drag.
Now lets pretend the drag is side wind.
I conclude there are 2 mediums in contact with the vehicle but those 2
have 2 directions each. This gives us 4 directions to work in rather
then just having drag.
^_^
http://gabydewilde.googlepages.com/negative-drag
gabydewilde - negative drag
wrote:
> "Vince Morgan" <vinharAtHereoptusnet.com.au> wrote in message
> news:[email protected]...
> > "CWatters" <[email protected]> wrote in message
> >news:[email protected]...
> > > "Elmo" <[email protected]> wrote in message
> > >news:[email protected]...
> > > > Of course what would really happen is that the wind would initially
> > blow
> > > > you backwards slightly, the backwards motion causing the fan to rotate
> > > > backwards which would cause you to go backwards faster, causing the
> fan
> > > > to rotate faster and so on. The effect would snowball until you were
> > > > going backwards at the speed of sound.
>
> > > > elmo
>
> > > One of these can sail dead into wind....
>
> > >http://i.treehugger.com/images/2007-2-21/Windmill-Sailboat.jpg
>
> > It can? How is that possible?
> > Vince
>
> Why is it impossible? What physical laws does it break?
>
> A sailing boat can tack upwind. There is little difference. Think about two
> sailing boats on opposite tacks towing the same barge. The sail boats go
> back and forth but the barge can be towed directly up wind. Look down on a
> windmill from above and you see one blade going left to right and the other
> right to left.
>
> I believe there was a you tube clip somewhere on the web once.
>
> More examples and some discussion..http://www.boatdesign.net/forums/showthread.php?t=14182
Hey hello,
That's a great topic Colin. There is so much to learn here. I bet you
will be crying from laughter when you figure out this negative drag
topic.
I mean, almost everyone else is looking for excuses not to look? And
not looking equals not knowing. No matter how often one self proclaims
being an expert. At best they are experts at finding excuses not to
investigate things.
Down the wind the vehicle has contact with 2 mediums. We should
picture the vehicle as traveling inside the wind using the relatively
moving road as it's propulsion to be able to move down the wind
faster. Or move relative to the medium it sits in.
A poster in the topic above suggest the combination of going faster as
the wind and going directly up the wind. Apparently there are even a
lot of fly-cycles today. I've seen so much propeller driven crafts by
now I'm starting to think it would not require any extra parts to do a
little bit of both. One could both go twice as fast as the wind and
sail straight up the wind using the same rig.
I have a good idea how this guy's special windmill works.
http://www.sailwings.net
Peter Worsley - Wingsailing
http://www.sailwings.net/markone.html
Peter Worsley - Wingsailing Mark 1
http://www.sailwings.net/marktwo.html
Peter Worsley - Wingsailing
http://www.sailwings.net/tldescribed.html
Peter Worsley - Wingsailing
http://www.sailwings.net/wingelec.html
Peter Worsley - Wingsail/Electric
http://www.sailwings.net/article.html
Peter Worsley - Wingsailing
Nice stuff he has.
As a hint all I needed was to know we missed something rather foolish
while deploying the windmill in our imaginations.
But.......
....... if you can sail 45 degrees up the wind faster as you can sail
down it. Then why would we put the windmill straight up the wind! The
thing can stand under an angle and tack the blade up wind half a
rotation then have it capture the full wind over the other half. The
wind is still coming from straight ahead but it's pushing against the
side of the boat now!
This is how the blades stand while sailing up the wind.
http://i.treehugger.com/images/2007-2-21/Windmill-Sailboat.jpg
It's not facing forwards as that would subtract the wind force from
the kinetic energy.
I had already half figured this out with the vortex recumbent cone.
http://gabydewilde.googlepages.com/vortex-recumbent
gabydewilde - vortex recumbent
use side wind rather then drag.
Now lets pretend the drag is side wind.
I conclude there are 2 mediums in contact with the vehicle but those 2
have 2 directions each. This gives us 4 directions to work in rather
then just having drag.
^_^
http://gabydewilde.googlepages.com/negative-drag
gabydewilde - negative drag
V
Vince Morgan
Guest
"CWatters" <[email protected]> wrote in message
news:[email protected]...
>
> "Vince Morgan" <vinharAtHereoptusnet.com.au> wrote in message
> > It can? How is that possible?
> > Vince
> >
>
> Why is it impossible? What physical laws does it break?
>
> A sailing boat can tack upwind. There is little difference. Think about
two
> sailing boats on opposite tacks towing the same barge. The sail boats go
> back and forth but the barge can be towed directly up wind. Look down on
a
> windmill from above and you see one blade going left to right and the
other
> right to left.
>
> I believe there was a you tube clip somewhere on the web once.
>
> More examples and some discussion..
> http://www.boatdesign.net/forums/showthread.php?t=14182
>
>
I won't go into the laws of science, which I mistakenly did in another group
recently.
However, as a thought experiment alone it has problems. Consider the
following.
I'll use a land vehical rather than a boat as an example so as to eliminate
some complexity.
I take a test vehical and mount upon it a wind turbine (as seen in the
video) facing directly into the wind. However, when I get to my test
location, there is no wind. Then I think for a moment. What is the wind
anyway? I soon realize that if I am moving into what is otherwise still air
I have the exact equivalence of wind.
Armed with my new realization I give my test bed a hard push, it finds
itself now apparently in wind, so it accelerates away from me. As it
accelerates there appears to be more wind, so it continues to accelerate.
The wheels I used have very good high speed bearings that offer very little
resistance to motion so the vehical just keeps accelerating until the tips
of the turbine blades hit Mach1?
Vince
news:[email protected]...
>
> "Vince Morgan" <vinharAtHereoptusnet.com.au> wrote in message
> > It can? How is that possible?
> > Vince
> >
>
> Why is it impossible? What physical laws does it break?
>
> A sailing boat can tack upwind. There is little difference. Think about
two
> sailing boats on opposite tacks towing the same barge. The sail boats go
> back and forth but the barge can be towed directly up wind. Look down on
a
> windmill from above and you see one blade going left to right and the
other
> right to left.
>
> I believe there was a you tube clip somewhere on the web once.
>
> More examples and some discussion..
> http://www.boatdesign.net/forums/showthread.php?t=14182
>
>
I won't go into the laws of science, which I mistakenly did in another group
recently.
However, as a thought experiment alone it has problems. Consider the
following.
I'll use a land vehical rather than a boat as an example so as to eliminate
some complexity.
I take a test vehical and mount upon it a wind turbine (as seen in the
video) facing directly into the wind. However, when I get to my test
location, there is no wind. Then I think for a moment. What is the wind
anyway? I soon realize that if I am moving into what is otherwise still air
I have the exact equivalence of wind.
Armed with my new realization I give my test bed a hard push, it finds
itself now apparently in wind, so it accelerates away from me. As it
accelerates there appears to be more wind, so it continues to accelerate.
The wheels I used have very good high speed bearings that offer very little
resistance to motion so the vehical just keeps accelerating until the tips
of the turbine blades hit Mach1?
Vince
C
CWatters
Guest
"Vince Morgan" <vinharAtHereoptusnet.com.au> wrote in message
news:[email protected]...
> "CWatters" <[email protected]> wrote in message
> news:[email protected]...
> I take a test vehical and mount upon it a wind turbine (as seen in the
> video) facing directly into the wind. However, when I get to my test
> location, there is no wind. Then I think for a moment. What is the wind
> anyway? I soon realize that if I am moving into what is otherwise still
air
> I have the exact equivalence of wind.
> Armed with my new realization I give my test bed a hard push, it finds
> itself now apparently in wind, so it accelerates away from me. As it
> accelerates there appears to be more wind, so it continues to accelerate.
> The wheels I used have very good high speed bearings that offer very
little
> resistance to motion so the vehical just keeps accelerating until the tips
> of the turbine blades hit Mach1?
> Vince
There is a difference. In one there is no relative movement between air and
land.
Sailing boats also experience "apparent wind" and can sail faster than the
real wind.
news:[email protected]...
> "CWatters" <[email protected]> wrote in message
> news:[email protected]...
> I take a test vehical and mount upon it a wind turbine (as seen in the
> video) facing directly into the wind. However, when I get to my test
> location, there is no wind. Then I think for a moment. What is the wind
> anyway? I soon realize that if I am moving into what is otherwise still
air
> I have the exact equivalence of wind.
> Armed with my new realization I give my test bed a hard push, it finds
> itself now apparently in wind, so it accelerates away from me. As it
> accelerates there appears to be more wind, so it continues to accelerate.
> The wheels I used have very good high speed bearings that offer very
little
> resistance to motion so the vehical just keeps accelerating until the tips
> of the turbine blades hit Mach1?
> Vince
There is a difference. In one there is no relative movement between air and
land.
Sailing boats also experience "apparent wind" and can sail faster than the
real wind.
D
datakoll
Guest
raise the jibs'l Mr Morgan
II. The relationship between an object's mass m, its acceleration a,
and the applied force F is F = ma. Acceleration and force are vectors
(as indicated by their symbols being displayed in slant bold font); in
this law the direction of the force vector is the same as the
direction of the acceleration vector.
This (preceeding) is the most powerful of Newton's three Laws, because
it allows quantitative calculations of dynamics: how do velocities
change when forces are applied. Notice the fundamental difference
between Newton's 2nd Law and the dynamics of Aristotle: according to
Newton, a force causes only a change in velocity (an acceleration); it
does not maintain the velocity as Aristotle held.
This is sometimes summarized by saying that under Newton, F = ma, but
under Aristotle F = mv, where v is the velocity. Thus, according to
Aristotle there is only a velocity if there is a force, but according
to Newton an object with a certain velocity maintains that velocity
unless a force acts on it to cause an acceleration (that is, a change
in the velocity). As we have noted earlier in conjunction with the
discussion of Galileo, Aristotle's view seems to be more in accord
with common sense, but that is because of a failure to appreciate the
role played by frictional forces. Once account is taken of all forces
acting in a given situation it is the dynamics of Galileo and Newton,
not of Aristotle, that are found to be in accord with the
observations.
III. For every action there is an equal and opposite reaction.
unless a force acts on it to cause an acceleration (that is, a change
in the velocity), as above to the extant of law lll
Otherwise, chaos
The overall theory, an expanding universe will collapse.
II. The relationship between an object's mass m, its acceleration a,
and the applied force F is F = ma. Acceleration and force are vectors
(as indicated by their symbols being displayed in slant bold font); in
this law the direction of the force vector is the same as the
direction of the acceleration vector.
This (preceeding) is the most powerful of Newton's three Laws, because
it allows quantitative calculations of dynamics: how do velocities
change when forces are applied. Notice the fundamental difference
between Newton's 2nd Law and the dynamics of Aristotle: according to
Newton, a force causes only a change in velocity (an acceleration); it
does not maintain the velocity as Aristotle held.
This is sometimes summarized by saying that under Newton, F = ma, but
under Aristotle F = mv, where v is the velocity. Thus, according to
Aristotle there is only a velocity if there is a force, but according
to Newton an object with a certain velocity maintains that velocity
unless a force acts on it to cause an acceleration (that is, a change
in the velocity). As we have noted earlier in conjunction with the
discussion of Galileo, Aristotle's view seems to be more in accord
with common sense, but that is because of a failure to appreciate the
role played by frictional forces. Once account is taken of all forces
acting in a given situation it is the dynamics of Galileo and Newton,
not of Aristotle, that are found to be in accord with the
observations.
III. For every action there is an equal and opposite reaction.
unless a force acts on it to cause an acceleration (that is, a change
in the velocity), as above to the extant of law lll
Otherwise, chaos
The overall theory, an expanding universe will collapse.
