posted by Aly on .
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?
I'm not going to do all of your homework for you. Show some work of your own and someone will critique it.
(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?
Please show me where I am going wrong.