How much total mechanical work does a eight lifter do in 10 repetitions

[ShakeWell]

ok, tell me if I'm wrong:

the questions asks:
How much total mechanical work does a eight lifter do in 10 repetitions of lifting (and lowering) 200 kg to a height of 1.0m?

I'm thinking, since the final total displacement is zero, the answer is 0 right?

 

[HallsofIvy]

The "total mechanical work" is the change in potential energy (and here, since the weight is returned to its initial position that is 0) only for a "conservative" force (i.e. no friction). Of course, gravity is conservative but, in general, the force supplied by muscles is not. I don't think it is possible to give a definite answer without knowing precisely what assumptions are made. Exactly what the total mechanical work is depends a lot on how it is moved. Many texts would not call the work the muscles have to do "mechanical" work. While I think there is a very good argument for "0 work", I recommend you discuss this with your teacher!

 

[M98Ranger]

Yes, you are correct. The total mechanical work done by the eight lifter in 10 repetitions would be 0, since the final displacement is zero. This is because work is defined as the product of force and displacement in the direction of the force. Since the weight is being lifted and lowered to the same height, the total displacement is zero and therefore the total work done is also zero.