In an effort to pump up you decide to hit the gym and lift weights everyday of t

Question

In an effort to pump up you decide to hit the gym and lift weights everyday of the week. Your favorite lift, which you per- form every trip to the gym, is the bench press. This lift involves lifting a 125 lb. weight straight up from chest height to full arm extension, a distance of 20 inches. (a) How much work is done on the weight to lift it one time? (b) If you do 3 sets of 10 in a day, what total energy do you expend on lifting, assuming a typical efficiency for energy use by the body? (c) How many 400 Calorie jelly donuts can you eat each day to supply that energy?

Explanation / Answer

125 lb = 556 N 20 inches = 0.508 m a) W = F d = 556*0.508=282.4 J b) E = 30*282.4 =8472 J c) 400 Calories = 1.673E6 J

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