(adsbygoogle = window.adsbygoogle || []).push({}); Question

A 75kg man jumpst from a window 1.0m above the side walk.

a) What is his speed just before his feet strike the pavement?

b) If the man jumps with his knees and ankles locked, the only cushion for his fall is approximately 0.50 cm in the pads of his feet. Calculate the average force exerted on him by the ground in this situation.

Work

a) MEi = MEf

PEi + KEi = PEf + KEf ===> mgh + (.5)mv^2 = mgh + (.5)mv^2

After plugging in values:

736 + 0 = 0 + 37.5v^2 ===> V^2 = 19.6 ===> V = 4.43 m/s

b) I'm not sure how to approach this problem. I assume I'm basically trying to find the normal force of the man....but I don't know what the height really has to do with the problem unless I'm supposed to use energies to relate to the force in some way.

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Force/Energy Problem

**Physics Forums | Science Articles, Homework Help, Discussion**