Work done against gravity when object is moving up
Answers
Case I: you apply a horizontal force (relatively small one) on the object and you let go. The object is set in motion, but because the surface is frictionless, the object stays in motion with no change in its velocity. All gravity does in this situation is hold the object on the surface. There is no displacement and therefor the WORK done is zero.
Case II: the force in (1) is applied but the exertion was sustained. The object will accelerate horizontally. The horizontal force’s vertical component is ZERO because it is equal to F cos theta and theta is 90 d. the the component is zero and all gravity does is hold the object on the surface. There is zero force and zero vertical displacement and Work is zero.
Case III: when useful work is done against gravity, a VERTICAL displacement is required. The problem is along a HORIZONTAL frictionless surface. So there is no vertical displacement and therefor there is zero work done..
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