While running a person transforms about `0.60 J` chemical energy to mechanical energy per stop per kilogram of body mass. If a `60 kg` runner transform energy at a rate of `72 W` during a race, how fast is the person running? Assume that a running step is `1.5m` long

Options

A. `2.0 m//s`
B. `3.0 m//s`
C. `2.5 m//s`
D. `sqrt((6 gh)/(13))`

Answer

D

Explanation

We first determine the energy output of the runner:
`= (0.60 J//kg - step) (60 kg) ((1 step)/(1.50 m)) = 24.0 J//m`
From this we calculate the force exerted by the runner per step:
`F = (24 J//m) (1 N.m//J) = 24 N`