Question

Assertion: Two balls are projected from the top of tower at the same instant. The ball $A$ is thrown horizontally with non-zero initial velocity while $B$ is dropped from rest. In this case both the balls reach the ground simultaneously.

Reason: The vertical motion of the two balls described in the above statement are identical.

• A. both assertion and reason are true and reason is the correct explanation of assertion.
• B. both assertion and reason are true but reason is not the correct explanation of assertion.
• C. assertion is true but reason is false.
• D. assertion is false but reason is true.

Answer 1

The correct option is A

both assertion and reason are true and reason is the correct explanation of assertion.

Explanation for assertion statement:

A diagrammatic representation of ball A was thrown from the tower is given below:

Here, $u$ is the initial velocity, $a$ is the acceleration and $g$ is gravity.

A diagrammatic representation of ball B thrown from the tower is given below:

Here, $u_x$ and $u_y$ are the horizontal and vertical components of the initial velocity, $a$ is the acceleration and $g$ is gravity.

It is true that both the balls will reach the ground at the same instant.

Explanation for reason statement:

1. The magnitude of the vertical components of the initial velocities of both the balls are zero and acceleration acting on it in the vertical direction is also the same.
2. Hence, the vertical motions of the two balls are identical is the true and correct reason for the assertion statement.
3. Therefore, the assertion and reason are true.

Hence, option A is the correct answer.