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

A weightlifter works out at the gym each day. Part of her routine is to lie on her back and lift a 41 kg barbell straight up from chest height to full arm extension, a distance of 0.55 m .

1. How much work does the weightlifter do to lift the barbell one time?

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

3. How many 430 Calorie donuts can she eat a day to supply that energy? Express your answer using two significant figures.

Solutions

Expert Solution

Solution:-

A weightlifter works out at the gym each day, part of her routine is to lie on her back and lift a 41kg barbell straight up from chest height and to full arm extension a distance of 0.55m

) Calculate work does the weightlifter do to lift the barbell one time

Work = force * distance

Weight = 41*9.8

Work = 41*9.8*0.55

Work = 220.99N-m

Work = 221 J

2) If the weightlifter does 25 repetitions a day , calculate total energy,

Work = Energy

Energy = (220.99J/rep)*(25rep)

Energy = 5524.75

Energy = 5525J if 100% efficiency

Since she is only 25% effiecincy she has to expend

4*5524.75J

= 22099 J

22099J of energy to do 5524.75 J of work.

3) How many 430 calories donuts can she eat a day to supply that energy

4.18J = 1 Calorie

22099/4.18 = 5286.84calories/430donuts = 12.29 donuts

12 donuts (two significant figures)

genius_generous answered 1 year ago

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