Question

A greased block P may slide along any of the three frictionless slopes A,B or C , to reach the ground. The work done on the block by block's weight Mg , are $${{W}_{\begin{smallmatrix}
A \\

\end{smallmatrix}}}$,${{W}{B}}$AND${{W}{C}}$the three slopes respectively. Then : (A)${{W}{A}}<{{W}{B}}<{{W}{C}}$(B)${{W}{A}}>{{W}{B}}>{{W}{C}}$(C)${{W}{A}}={{W}{B}}={{W}_{C}}$$
(D) NONE OF THE ABOVE

Answer 1

the block is greased and on all the three parts there is no friction. So, we do not have to consider frictional force. We need to find the work done by weight. Weight is nothing but the gravitational force with which earth pulls a body towards itself

Complete step by step answer: Here we have to find out the work done by the gravitational force. We know that gravitational force is a conservative force and work done by the conservative force does not depend upon the path taken by the body.
Also, the distance measured for all the three paths A, B, and c are the same. We know work is given as the product of force and displacement. In all the three cases force is the same viz gravitational force and the displacement to be covered is also the same, hence, the work done in all the three cases must be equal. So, the correct option is (C).

Additional Information: A conservative force is a force with the property that the total work done in moving a particle between two points is independent of the taken path

Note: if there was present friction in any of the three paths then our answer would have certainly changed because we will also have to consider frictional force and there we have to do work against the frictional force because frictional force always opposes the motion.