# Work power and energy by a weight lifter

## Homework Statement

A weight lifter (mass 75Kg) raises body's centre of mass by 0.4 in the process of lifting a barbell weight of 70kg to the height of 1.04m above the ground. Calculate the total work done in lifting the weight.The weight is raised in 0.2 seconds; hence calculate the power of the weight lifter.

## Homework Equations

m x a = f
F x s = work
Power= work done/time taken

## The Attempt at a Solution

70kg X 9.81 m/s = 686.7N
work= 686.7 X 1.04=714.168 j
How do i work out the distance travelled? the weight lifter wouldn't lift a barbell 1.04m.
power =714.168/0.2=1373.4 W

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tiny-tim
Homework Helper
welcome to pf!

hi ridsyfootball! welcome to pf! … How do i work out the distance travelled? the weight lifter wouldn't lift a barbell 1.04m.
i don't understand … that's about chest-height … what's worrying you about that? (and don't forget to add the work done by raising his own mass )

sorry my first post was deleted as i gave u a straight answer
so,

write the coordinates of CM before and after lifting the weight

solve them and u can het the answer

thanks for the help guys i understand now and iv got what i think is the correct answer.