A person lifts a 8.2 kg box of bricks a vertical distance of 1.30 m and then carries the box horizontally a distance of 11.00 m.

Question

(a) How much work is done by the person in the process?



(b) How much work is done by gravity in the process?

Answer 1

There is only a basis for work for applying a force vertically and moving vertically. The horizontal motion at right angles to the direction of the exerted force is not work (W = Fdcosθ)

F exerted upward is equal to the weight, so the work is mgh = 8.2kg x 9.8 N/kg x 1.3 m = ___ J

The work done by gravity is the negative of this as the force of gravity is directed in the opposite direction of the displacement (negative work)

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