Question

From the top of tower of height $200m$, a ball $A$ is projected up with speed $10m{s}^{-1}$ and $2s$ later, another ball B is projected vertically down with the same speed. Then

• A. Bath A and B will reach the ground simultaneously.
• B. Ball A will hit the ground $2s$ later then B hitting the ground.
• C. Bath the balls will hit the ground with the same velocity.
• D. Bath will rebound to the same height from the ground, if both have same coefficient of restitution.

Answer 1

Answer: (A), (C), (D)

The correct options are
A Bath A and B will reach the ground simultaneously.
C Bath the balls will hit the ground with the same velocity.
D Bath will rebound to the same height from the ground, if both have same coefficient of restitution.

For ball $A$,

$T_f=\frac{2u}{g}$

$=\frac{2\times 10}{10}=2s.$

Therefore after $2s$, $Pt$ will reach the point at which $Pt$ thrown. But $P{t}^{\prime }s$ velocity will be same but opposite $Pn$ direction, i.e, downward.

$\therefore$ The ball $A$ & $B$ starts falling from same height with same velocity.

$\therefore$ They will reach the ground at same time and with same velocity.

It their properties are same, they will be bound to the same height.