Block A has no relative motion with resprct to wedge fixed to the lift as shown in figure during motion-1 or motion-2 Then,

Options

A. work done by gravity on block A in motion-2 is less then in motion-1
B. wrok done by normal reaction on block A in both be motions will be positive.
C. work done by force of friction in motion-1 may be positive.
D. work done by force of friction in motion-1 may be positive.

Answer

A, B, C, D

Explanation

(a) Work done by gravity in motion 1 is zero `(theta=90^@)` and in motion 2 is negative `(theta=180^@)`
(b) In both cases angle between N and S is acute.
(c) and (d) Depnding on the act upnthe plane or down the plane. Therefore angle between friction and displacement may be obtuse ot acute. So, work done by friction may be negtive or positive.