This question came in the Rajshahi University admission exam in 2014-15
Q) Which one is true in the case of conservative force?
(A) Energy is wasted
(B) The work done cannot be regained
(C) The law of conservation of mechanical energy is not conserved
(D) None of the above
My interpretation of B
When we throw a ball vertically upwards and it comes back to us after some time, the total work done by the force of gravity on the ball is zero, so the force of gravity is a conservative force. When the ball is thrown upwards, then negative work is done on the ball by the force of gravity in the first half, and then positive work is done by the force of gravity on the ball: the work done is "regained".
On the contrary, when we move a box along a surface that has friction, no matter in which direction we push the box, the work done by the frictional force on the ball is negative. So, the work done is always negative in the case of non-conservative forces, unlike conservative forces. So, we can say that the work done cannot be regained.
(A) and (C) are clearly wrong. According to my explanation, (B) should also be wrong. So, (D) should be the correct answer.
However, the question bank says that the correct answer is (B). Why is it saying that?