Question

physics10

While running, a person dissipates about 0.6 J of mechanical energy per step per kilogram of body mass. If a 60-kg person runs with a power of 70 Watts during a race, how fast is the person running? Assume a running step is 1.5 m long.

Answer 1

power dissipation for each step and for each kilogram is 0.6 J

P = m*g*h/t = 0.6 J

but power of the running person is 70 W

for 1 kg power dissiation is 0.6 J

For 60 kg power dissipation is 0.6*60 = 36 J for each step

So 70 J is for 36/70 = 0.515 steps per second = 0.515*1.5 = 0.77 m/s