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For a moving body at any instant of time
If the body is not moving, the acceleration is necessarily zero
If the body is slowing, the retardation is negative
If the body is slowing, the distance is negative
If displacement, velocity and acceleration at that instant are known, we can find the displacement at any given time in future
Solution
$(A)$ Suppose throwing a ball vertically up. At the highest point. It is at momentary rest $( V = O )$ i but acceleration $g$ still acts downwards. So, (A) is incorrect.
$(B)$ A slowing body has positive retardation.
$(C)$ Distance travelled is always positive, irrespective its motion.
$(D)$ From second law of kinematics,
$x=x_0+u t+\frac{1}{2} a^2$
By knowing $u , a$ and $x _0$ at instant $t =0$ we can determine $x$ at any $t$.
