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Three part weightlifter question

  • #1

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 ???/
 

Answers and Replies

  • #2
390
1
Use the work energy theorem, the barbell has zero velocity at both the top and bottom of the rep.
 
  • #3
I like Serena
Homework Helper
6,577
176
Your acceleration "a" is the acceleration of gravity: g=9.8 m/s2.
With what you already have you should be able to find the work w...
 

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