Question

Two identical balls are released at the same time from a building of height $85m$, one from the top while the other from half way up.
Which of the following quantities is same for both balls?

• A. Time of travel
• B. Final speed
• C. Acceleration
• D. Total displacement

Answer 1

Answer: (C)

Acceleration

As, they are released from a building, so same acceleration will act upon both the balls, that is, g(acceleration due to gravity) and it's the same for both cases.

given: initial velocity, $u=0$

Final velocity, $v^2-u^2=2gh$

$v^2=2gh$

as the height of dropping the balls is different, so the final velocity and speed will be different for both.

Total displacement will be different as both are dropped from a different height, height will be the displacement in this case.

Time of travel,

$s=ut+\left(1/2\right)g{t}^2$

Solving for t,

$t=\sqrt{\frac{2h}{g}}$.

As heights are different, so, time taken to reach the ground will be different.
Hence, the correct option is $\left(C\right)$