A weightlifter works out at the gym each day. Part of her routine is to lie on h

Question

A weightlifter works out at the gym each day. Part of her routine is to lie on her back and lift a 43 kg barbell straight up from chest height to full arm extension, a distance of 0.47 m .

Part A How much work does the weightlifter do to lift the barbell one time?

Part B If the weightlifter does 24 repetitions a day, what total energy does she expend on lifting, assuming a typical efficiency for energy use by the body (25%).

Part C How many 460 Calorie donuts can she eat a day to supply that energy?

Explanation / Answer

1) work done to lift the barbell in one time=W = mg H = 43*9.8*0.47 = 198.1 J

2) in a day the total work done=Et = 24*W/0.25 = 96*198.1 = 19014 J

3) no of donuts she eat= 19014/(460*4.184) = 9.88 =10

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