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Work power and energy by a weight lifter

  • #1

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
 

Answers and Replies

  • #2
tiny-tim
Science Advisor
Homework Helper
25,832
250
welcome to pf!

hi ridsyfootball! welcome to pf! :smile:
… 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:)
 
  • #3
1,137
0
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
 
  • #4
thanks for the help guys i understand now and iv got what i think is the correct answer.
 

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