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 40 { m kg} barbell straight up from chest height to full arm extension, a distance of 0.55 { m m}.

Part A
How much work does the weightlifter do to lift the barbell one time?
Express your answer using two significant figures.

Part B
If the weightlifter does 17 repetitions a day, what total energy does she expend on lifting? Assume 25 % efficiency.

Part C
How many 480 Calorie donuts can she eat a day to supply that energy?
Express your answer using two significant figures.
Express your answer using two significant figures.

Explanation / Answer

I has having a really hard time finding the correct answer for part C.

It seems that the issue everyone is having is failing to recognize that:

1 calorie = 4.184 KJ

So, 1 calorie = 4184 J

Once this is accounted for:

14660.8 J / (480 * 4184) = 0.007300032

OR

7.3x10^-3 donuts

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