Question

If a 0.200-kilogram ball sits on a shelf 2.00 meters from the floor, how much mechanical energy (ME) does it possess?

Answer 1

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its potential energy is 0.2*9.8*2 = 3.92 J
no work is being done on the object (normal force of shelf up is counteracting force due to gravity down), so its mechanical energy is zero.
the mechanical energy that was required to lift the ball from the floor to the shelf is the same as its present potential energy, or 3.92 J.
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