A mass of 10 kg is at a point A on a table. It is moved to a point B. If the line joining A and B is horizontal, what is the work done on the object by the gravitational force? Explain your answer.

Given,

Mass (m) = 10 kg

Work done by gravity depends on the vertical displacement of the body. It is independent of the horizontal path.

So, work done by gravity is = m g h

Where,

Vertical displacement, h = 0 [∵ the line joining A and B is horizontal. ]

∴ W = m × g × 0 = 0

Hence, work done on object by gravity is zero.