# Multi particle system

1. Nov 19, 2008

### lebprince

1. The problem statement, all variables and given/known data

A runner whose mass is 49 kg accelerates from a stop to a speed of 6 m/s in 2 seconds. (A good sprinter can run 100 meters in about 10 seconds, with an average speed of 10 m/s.)

(a) What is the average horizontal component of the force that the ground exerts on the runner's shoes? I got the answer for this which is 147 N.

(b) How much displacement is there of the force that acts on the sole of the runner's shoes, assuming that there is no slipping? I got the answer for this one too = 0 m

(c) Therefore, how much work is done on the real system (the runner) by the force you calculated in part (b)? I also got 0 for this one since its F x d

(d) How much work is done on the point-particle system by this force? (Hint: use a fundamental principle, as applied to the point-particle system.)

3. The attempt at a solution

I got a,b,c am just having problems with part d. Thanks a lot

2. Nov 19, 2008

### lebprince

figured it out thanks