Question

Two balls are projected simultaneously with the same velocity u from the top of a tower, one vertically upwards and the other vertically downwards. Their respective times of the journeys are $t_1$ and $t_2$ . At the time of reaching the ground, the ratio of their final velocities is

• A. 1:1
• B. 1:2
• C. 2:3
• D. 2:1

Answer 1

Answer: (A)

Using: $v^2=u^2+2aS$
where, v final velocity, u initial velocity a is acceleration and S is displacement of the particle.
For particle $1:v_1^2=u_1^2+2(-g)(-h)$ taking upward direction positive
For particle $2:v_2^2=u_2^2+2(-g)(-h)$
as $u_1=u_2$ and displacement of both the particle is equal to height of tower, their velocities at time of reaching ground will be equal.