Question

Work done by normal reaction is zero during the motion of the block:

• A. from point $A$ to $B$ only
• B. from point $B$ to $C$ only
• C. from $A$ to $C$
• D. None of these

Answer 1

The correct option is C from $A$ to $C$

Given: A small block m is released from point A on a fixed smooth wedge as shown in figure. Bottom of wedge is marked as B and at a point C the block stops moving because the straight part of floor is rough

To find work done by normal reaction is zero during the motion of the block

Solution:

Normal reaction is always perpendicular to the direction of motion.

That means that the work done by normal reaction is always zero from point A to C since it is always perpendicular to the displacement of the block.

Hence work done by normal reaction is zero during the motion of the block will be from A to C.