Question

List-I shows some arrangements in which motion of masses are described and list-II defines motion of centre of
mass of the system ($m+M$).
Match appropriate possible options in list-II

List-I	List-II
(p) Person moves with constant acceleration (towards right)	1. Centre of mass must remain at rest
(q) At $t=0$, a person at point A is moving with constant velocity (towards right) and the plank is at rest , then for his motion between point A and B.	2. Centre of mass must move with constan velocity
(r)	3. Acceleration of centre of mass may be zero.
(s)	4. Centre of mass must have a component of acceleration in the downward direction

• A. p - 3, q - 1, r - 2, s - 4
• B. p - 3, q - 2, r - 1, s - 4
• C. p - 4, q - 2, r - 1, s - 3
• D. p - 4, q - 1, r - 2, s - 3

Answer 1

The correct option is B p - 3, q - 2, r - 1, s - 4

(P) Since external force in horizontal direction is zero there for COM remains at rest.
(Q) If the block remains at rest then centre of mass moves with constant velocity.
(R) If $m$ does not slip on $M$ then COM remains at rest otherwise COM is accelerated when m moves from
point A to B.
(S) The COM is accelerated vertically downwards by the gravity force.