Q: Which statements can be possible cases in one/two dimensional motion:
(A) A body has zero velocity and still be accelerating
(B) The velocity of an object reverses direction when acceleration is constant
(C) An object be increasing in speed as its acceleration decreases
(D) None of these
Solution : (a) When the body is projected vertically up, at the highest point its speed becomes zero whereas it is accelerating downwards with g = 9.8 m/s2.
(b) When a body is projected up, the velocity during ascent reverses its direction during its descent, whereas the acceleration of the body remains constant, that is g .
(c) Acceleration means, increasing speed (magnitude of velocity). Therefore, the speed of a particle increases with an acceleration. When the acceleration is decreased the speed of the particle goes on decreasing till the acceleration reduces to zero.
Ans: (A) and (B)