Physics - W.E.P. Question with Solution | TestHub
Column-I shows constrained motion of a particle in vertical plane. The constraint force (tension and normal reaction) are collectively denoted by F. Match the characteristic shown in column-II with that in column-I. Consider the motion by the time the particle returns to starting point or comes to permanently at rest.
Column-I | Column-II |
|---|---|
(A)
A particle is projected inside a smooth tube, it fits slightly loosely inside it. | |
(B)
A bob constrained on a string. | |
(C)
A bob constrained on a rod. | |
(D)
A small block is projected inside a spherical ball along the inner surface. |
Options:
Answer:
Solution:
(A) Tube with slightly loose fit: either wall can push, so the constraint force may be directed radially outward (P). At the lowest point (and whenever the constraint force vanishes) the net of constraint force and gravity is purely centripetal (Q). With
the speed decreases monotonically until the particle momentarily stops at the top, so the tangential acceleration reduces the speed for the entire motion considered (R); it does not complete a sustained circular revolution (not S).
(B) A string can only pull (radially inward), never outward (not P). With
the bob rises only to height R and the string slackens; the motion is not circular throughout and the speed does not decrease for the entire motion (not R, not S). (Q) holds at the lowest point.
(C) A rod can pull or push, so the constraint force may be radially outward (P). With
the bob cannot reach the top, so it oscillates (not S) and the tangential acceleration does not decrease the speed for the entire motion (not R). (Q) holds.
(D) The inner surface of the ball can only push radially inward (not P). With
the block completes the circular path (S). (Q) holds.
Answer: A - PQR, B - Q, C - PQ, D - QS (option A).
