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You are asked to push two wheelbarrows up a hill. One wheelbarrow is empty, and you are...

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sultanbaloch | Student, Undergraduate | (Level 2) eNoter

Posted May 7, 2013 at 6:39 PM via web

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You are asked to push two wheelbarrows up a hill. One wheelbarrow is empty, and you are able to push it up the hill in one minute. The other isfilled with huge rocks,and even after you push it for an hour, you cannot budge it. In which case do you do more work on the wheelbarrow, elaborate your answer?

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ishpiro | Teacher | (Level 2) Associate Educator

Posted May 8, 2013 at 2:00 AM (Answer #1)

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You do more work on the empty wheelbarrow, the first case.

The work of a given force on an object equals the product of the force (more precisely, the component of the force in the direction of the motion of the object) and the distance traveled by the object.

In the first case, the force on the empty wheelbarrow, however small, is non-zero, and the distance traveled by the wheelbarrow is non-zero. So the work done is non-zero.

In the second case, the force applied to the wheelbarrow is large, but the wheelbarrow does not move, so it travels zero distance. This means the work, which is force times distance, is zero.

Therefore, you do more work in the first case.

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