Question

A ball is thrown vertically upwards with an initial speed of 20 ms\(^{-1}\). The velocity (in ms\(^{-1}\)) and acceleration (in ms\(^{-2}\)) at the highest point of its motion are respectively:

• A. 20 and 9.8
• B. 0 and 9.8
• C. 0 and 0
• D. 10 and 9.8
• E. 0 and 4.9

Hint:

At the highest point of motion in vertical projectile motion, the velocity becomes zero, but the acceleration due to gravity remains \( 9.8 \, {ms}^{-2} \) downward.

Answer 1

The Correct Option is B

When a ball is thrown vertically upwards, its velocity decreases due to the acceleration due to gravity, which acts in the downward direction. At the highest point of its motion, the velocity of the ball becomes zero because it momentarily stops before reversing direction and starting to fall back down.
Thus, at the highest point:
- The velocity is \( 0 \, {ms}^{-1} \).
- The acceleration is still due to gravity, which is constant and equal to \( 9.8 \, {ms}^{-2} \) in the downward direction.
Thus, the correct answer is option (B), 0 and 9.8.