physics  runner
posted by lau .
While running, a person dissipates about 0.60 J of mechanical energy per step per kilogram of body mass. If a 60 kg person develops a power of 78 W during a race, how fast is the person running? (Assume a running step is 1.5 m long.)

.6 j/(step kg) *60 kg = 36 j/step
36 j/step *1 step/1.5 m = 24 J/m
24 J/m * v m/s = 24 v J/s or 24 v watts
24 v watts = 78 watts
v = 78/24 = 3.25 meters/second 
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