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PHY 121
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** Question Form_labelMessages **
Chapter 6, Question 4
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The problem is: How much work did the movers do horizontally pushing a 160 kg crate 10.3 m across a rough floor without acceleration, if the effective coefficient of friction was 0.50?
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I am stumped on this one because of the no acceleration part. I have `dw = F`ds and F=m*a. Mass is 160 kg and displacement is 10.3 m. However, if the acceleration is 0, then the whole thing becomes zero.
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This doesn't make sense because they obviously did work to move the box against the force of friction. However, if acceleration is zero, the whole thing falls apart.
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You can do a lot of work pushing or pulling things at a constant velocity, which is a zero-acceleration state.
No acceleration means that the crate's velocity remains constant, and that the net force on it is zero.
The force you exert is therefore equal and opposite to the frictional force, no more and no less.
Newton's First Law says that an object in motion will remain in motion with no change in speed or direction unless acted on by a nonzero net force. That is the case here. Because of friction, it is necessary to exert the equal and opposite force to achieve this state.
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