GK
PHYSICS
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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True
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False
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Either A or B
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None of the above
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Detailed explanation-1: -There is no displacement of weight when he holds it. Hence, no work is done.
Detailed explanation-2: -As you are lifting the object you are doing work on the object. The work W done on an object by a constant force is defined as W = F·d. It is equal to the magnitude of the force, multiplied by the distance the object moves in the direction of the force.
Detailed explanation-3: -Work Requires Motion The weight lifter does no work on the barbell as he holds it over his head. The force applied to the barbell does not cause it to move.
Detailed explanation-4: -A barbell lifted high above a weightlifter’s head possesses mechanical energy due to its vertical position above the ground (gravitational potential energy). A drawn bow possesses mechanical energy due to its stretched position (elastic potential energy).
Detailed explanation-5: -If you hold it over your head, it is not changing distance, and thus you are not performing work. Just because something has potential energy, doesn’t mean that work is being done on it-you have gravitational potential energy right now, but no work is being done unless you move through space.