Question

A ball of mass 500 g strikes a fixed wall with a speed of 10 m/s. After striking, it returns back with the same speed. Find the magnitude of the change in momentum of the ball.

• A. 0 kg m/s
• B. 5 kg m/s
• C. 10 kg m/s
• D. 15 kg m/s

Answer 1

The correct option is C 10 kg m/s

Initial momentum, $p_i$ = m x $v_i$ = 0.5 kg x 10 m/s = 5 kg m/s

After the collision with the wall, the velocity of the ball becomes opposite to the initial velocity.
⇒ Final velocity, $v_f$ = -10 m/s
Here, the negative sign implies the opposite direction.

Final momentum, $p_f$ = m x $v_f$
= 0.5 kg x (-10 m/s) = -5 kg m/s

Change in momentum, Δp = $p_f$ - $p_i$
⇒ Δp = - 5 - 5 = - 10 kg m/s
Magnitude of the change in momentum = 10 kg m/s