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hexum
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Homework Statement
I am figuring out the physics of the scene in the movie Get Him to the Greek where an actor falls into a pool but breaks his arm by hitting it on the concrete edge.
Mass of actor = 73 kg
Mass of arm = 4.75 kg
Force to break an arm = 73 N
Duration of fall = 3.0 s
Homework Equations
average impact force = m* V/dT
height of fall = 1/2*9.8*3.02 = 44.1 m
The Attempt at a Solution
F = m V/dT = m sqrt(2gH)/dT = 4.75*sqrt(2*9.8*(44.1))/1 = 214.6
Because 214.6 N is obviously greater than 73 N, which is the force to break an arm, then the physics in this situation seem to be good. However, I am confused on how to calculate dT. As you can see, it is 1 in the equation, but I do not see why it is not 3, which is the total time of the fall. I am told that this is the "impact interval." How exactly am I suppose to calculate this?