# Physics

posted by .

A man drinks a bottle of beer and proposes to work off it's 460 kj by exercising with a 20-kg barbell. If each lift of the barbell from chest height to over his head is through 60 cm and the efficiceny of his body is 10 percent under these circumstances, how many times must he left the barbell?

• Physics -

I'm not going to do all of your homework for you. Show some work of your own and someone will critique it.

• Physics -

(460 kJ)(x) = (20kg)(9.8 m/s2)(.6 m)
460,000 J (x) = 117.6
460,000/117.6 = x
3912 times of lifting the barbell

But, here is where I lose it,

if it is 10% efficient, then wouldn't he have to do 10 times as much?

39120 lifts?

Please show me where I am going wrong.

## Respond to this Question

 First Name School Subject Your Answer

## Similar Questions

1. ### Science

A man drinks a bottle of beer and proposes to work off its 460 kj by exercising with a 20 kg barbell. If each lift of the barbell from chest height to over his head is through 60 cm and the efficiency of his body is 10 percent under …
2. ### Physics

A bodybuilder is holding a 32 kg steel barbell above her head. How much force would she have to exert if the barbell were lifted underwater?
3. ### physics pbs

A bodybuilder is holding a 20-kg steel barbell above her head. How much force would she have to exert if the barbell were lifted underwater?
4. ### Physical science

A man drinks a bottle of beer and proposes to work off it's 460 kj by exercising with a 20-kg barbell. If each lift of the barbell from chest height to over his head is through 60 cm and the efficiceny of his body is 10 percent under …
5. ### physics

A weightlifter holding a 500 kg barbell waist high carries the barbell at a constant height and a constant speed to a rack 2 m away, and places the barbell on the rack at the same height at which he was carrying it. How much work does …
6. ### physics

A weight lifter lits a 1250 pound barbell 2 meters in 3 seconds. How much power was used to lift the barbell
7. ### Science

A weight lifter lifts a barbell from the ground, raises it at a constat velocity and holds it motionless over his head. How does the force of the lifter compare with the wieght of the barbell at different stages of the lift?
8. ### Physics

the work done in lifting a 600-N barbell 1.6m above the floor. What is the gain of potential energy of the barbell when it is lifted to this height?
9. ### College Physics

(a) How many hours does it take him to work off a 450 Calorie bagel if he stays in bed all day?
10. ### Physics

A weight lifter is bench-pressing a barbell whose weight is 710 N. He raises the barbell a distance of 0.65 m above his chest then he lowers it at 0.27 m. Determine the work done on the barbell by the weight lifter during:a.)the lifting …

More Similar Questions