Question

0.2 kg ball strikes a wall with velocity \(10\,ms^{-1}\) and rebounds with \(8\,ms^{-1}\). The impulse delivered by the ball is}

• A. 0.4 Ns
• B. 3.6 Ns
• C. 1.4 Ns
• D. 1.8 Ns
• E. 16.0 Ns

Hint:

In rebound problems, final velocity must be taken with opposite sign because the direction changes.

Answer 1

The Correct Option is B

Impulse is equal to change in momentum: \[ J = m(v_f-v_i) \] Take initial velocity toward the wall as positive: \[ v_i=+10\,ms^{-1} \] After rebound, the direction reverses: \[ v_f=-8\,ms^{-1} \] So, \[ J=0.2(-8-10) \] \[ J=0.2(-18)=-3.6 \text{ Ns} \] Magnitude of impulse: \[ |J|=3.6\text{ Ns} \]
Hence, the correct answer is: \[ \boxed{(B)\ 3.6\text{ Ns}} \]