Question

A ball of mass 50 g moving with a velocity of 10 ms$^{-1}$ is hit by a bat and the ball retraces back with a velocity of 20 ms$^{-1}$. Then the impulse on the ball is

• A. 0.5 kg ms$^{-1}$
• B. 1.0 kg ms$^{-1}$
• C. 1.50 kg ms$^{-1}$
• D. 1.5 kg ms$^{-1}$

Hint:

Remember to consider direction when calculating change in velocity for impulse: $Impulse = m(v - u)$

Answer 1

The Correct Option is D

Mass $m = 50 \text{ g} = 0.05 \text{ kg}$
Initial velocity $u = 10$ ms$^{-1}$, final velocity $v = -20$ ms$^{-1}$ (since it reverses direction)
Impulse $= m(v - u) = 0.05(-20 - 10) = 0.05(-30) = -1.5$ kg ms$^{-1}$
Magnitude of impulse $= 1.5$ kg ms$^{-1}$