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## Homework Statement

A weightlifter works out at the gym each day. Part of her routine is to lie on her back and lift a 40kg barbell straight up at a distance of .50m.

a. how much work does the weightlifter do to lift the barbell one time?

b. if the weightlifter does 20 reps a day what total energy does she expend on lifting? assume 25% efficency.

c. How many 400 calorie donuts can she eat a day to supply that energy.

## Homework Equations

w=fd f=ma

## The Attempt at a Solution

w=fd w=f*.50m

f=40kg*a ???/