Work power and energy by a weight lifter

AI Thread Summary
A weight lifter with a mass of 75 kg raises a barbell weighing 70 kg to a height of 1.04 m, while also lifting his center of mass by 0.4 m. The force exerted is calculated as 686.7 N, leading to a total work done of 714.168 J. The power output of the lifter, calculated over a time of 0.2 seconds, is 1373.4 W. Discussion participants clarified the need to consider the distance traveled and the work done in lifting the lifter's own mass. The conversation concluded with a confirmation of understanding and a potential correct answer.
ridsyfootball
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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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welcome to pf!

hi ridsyfootball! welcome to pf! :smile:
ridsyfootball said:
… How do i work out the distance travelled? the weight lifter wouldn't lift a barbell 1.04m.

i don't understand :redface: … that's about chest-height … what's worrying you about that? :confused:

(and don't forget to add the work done by raising his own mass :wink:)
 
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.
 
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