A small ball of mass `m` is released from rest at a height `h_(1)` above ground at time `t = 0`. At time `t = t_(0)`, the ball again comes to rest at a height `h_(2)` above ground. Consider the ground to be perfectly rigid and neglect air friction. In the time interval from `t = 0` to `t = t_(0)`, pick up the correct statements.

Options

A. Work done by gravity on ball is `mg(h_(1) - h_(2))`
B. Work done by ground on ball for duration of contact is `mg (h_(1) - h_(2))`.
C. Average acceleration of the ball is zero.
D. Net work done on the ball by all forces except gravity is `mg(h_(1) - h_(2))`.

Answer

A, C, D

Explanation

From the figure-1 work done by gravity from `t = 0` to `t = t_(0)` is `W = mg`
`(h_(1) - h_(2))`

fixed horizontal surface
Since initial and `g` final velocity of ball is zero its average acceleration will be zero.
Since net work done is zero from time interval `t = 0` to `t = t0`. Hence work done by forcesz expect gravity is `mg(h_(2) - h_(1))`.