Quoted message said:From: Retro Bob [email hidden]
Quoted message said:If a 155 pound mass (me) is traveling at 10 mph (on bike) and I
strike an object dead on with my shoulder (roughly 2 sq inches) -
what the load presented by my shoulder to the object.
155 lbm ~= 70 kg
10 mph ~= 16 kph
16 kph = 16,000 m/h
16,000 m/h ~= 5,000 m/s
1/2 * 70 kg * (5,000 m/s)^2 ~- 90*10^6 kg*m/s^2
2 sq in ~= 12 cm^2
12 cm^2 = 12*10^-4 m^2
90*10^6 kg*m/s^2 / (12*10^-4 m^2) ~=
10.80*10^12 kg*m/2^2 / m^2
Sufficient to cause a nasty bruise.
To know the load in units of force per area requires an estimate of the contact
time.
This is merely an estimate of the maximum energy per unit area.
Quoted message said:A rough calculation of 150lbs concentrated into 2 sq inches tells
me that the static load would be 75 lbs/inch.
Yes, if the object were vertical and you did a pushup on it one handed, that
would be the load on your hand.
Quoted message said:. but obviously
the 10 mph would be the key here...
Yeah. Contact time and acceleration are key to understanding force. I know it
feels instantaneous, but varying the estimated contact time from 0.1 sec to
0.01 sec increases the estimated acceleration by 100 times. So an accurate
estimate of contact time is required to answer your question, and don't believe
any of us can come up with one.
What was the actual damage to your shoulder? We could back-estimate....
Quoted message said:I forgot more physics than
I ever really understood.
Me too.
But I do remember how to spel.
Yours,
Doug Goncz ( ftp://users.aol.com/DGoncz/incoming )
Student member SAE for one year.
I love: Dona, Jeff, Kim, Mom, Neelix, Tasha, and Teri, alphabetically.
I drive: A double-step Thunderbolt with 657% range.