Hey. Do you mind helping me out with this physics problem?
10. A 74 kg man drops to a concrete patio from a window only 0.50 m above the patio. He neglects to bend his knees on landing, taking 2.0 cm to stop.
(a) What is his average acceleration from when his feet first touch the patio to when he stops?
(b) What is the magnitude of the average stopping force?
I'm not really sure where/how to begin this problem, but I started calculating the time that it took him to fall:
x-x0 = v0t + 1/2 at^2
x-x0 = 1/2 at^2
t = sqrt(2(x-x0)/a) = sqrt(2(0.50)/9.8) = 0.319438282 s.
Then I went into a different direction. I looked at when the man is touching the patio for the first time:
^ F = ?
v mg = (74)(-9.8) = 725.2 N.
F = ma
F - 725.2 = (74)(a)
Now I'm stuck, because I don't know F nor a. Can anyone help me out?