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AAMC question 74
Lauren_6408
#1 Posted : Thursday, June 17, 2021 8:04:47 AM
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Hi there,
I was wondering if someone could explain why there is no need to include the angle in this calculation of work. I thought forces perpendicular to the displacement do not do any work. In this question then I thought W = Fdsin(60). Because the object is moving vertically rather than horizontal I chose sin instead of cos. (Not sure if the picture will show up).

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INSTR_Katrina_128
#2 Posted : Tuesday, June 22, 2021 8:35:42 PM
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OOOH this question is evil!!! 😫

In this case, when you are lifting the 4 kg mass, you are doing work AGAINST GRAVITY, so the distance being travelled by the mass for the purposes of the work calculation is 5 m directly up.

So, W = Fd = (4 kg)(10 m/s²)(5 m) = 200 J.

Therefore, D is the best answer to the question.

The angle has nothing to do with it because gravity is just straight up and down. 😣
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