Question

A 79-kg sprinter accelerates from rest to a speed of 11.0 m/s in 4.8 s.
(a) Calculate the mechanical work done by the sprinter during this time.
J

(b) Calculate the average power the sprinter must generate.
W

(c) If the sprinter converts food energy to mechanical energy with an efficiency of 25%, at what average rate is he burning Calories?


(d) What happens to the other 75% of the food energy being used?



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Answer 1

a. a = (V-Vo)/t = (11-0)/4.8=2.29 m/s^2.
d = 0.5a*t^2 = 0.5*2.29*(4.8)^2=26.4 m.
Work = F*d = mg*d = (79*9.8) * 26.4 =
20,439 J.

b. P = F*d/t = 20439/4.8 = 4258 J/s =
4258 W.