Late for his morning workout, a 65.0-kg man eats a 168.0-Calorie energy bar for
ID: 1998642 • Letter: L
Question
Late for his morning workout, a 65.0-kg man eats a 168.0-Calorie energy bar for breakfast. What is the energy equivalent of this energy bar in joules? On a stair-climbing exercise machine, each "step" can be thought of as increasing the gravitational potential energy of the man-Earth system. If the equivalent height of each step is 12.0 cm, how many steps must the man take to work off the energy of the energy bar? Assume the efficiency of the human body in converting chemical energy to mechanical energy is 20.0%.Explanation / Answer
a) energy = 168*4.184 = 702.9 J
b) number of steps = 0.20*702.9/[65*9.8*0.12]
= 1.84 steps
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