Impulse-momentum theorem

Steps:

• Initial momentum of stationary ball is 0.
• Final momentum is m v.
• Change in momentum Δp = m v - 0 = m v.
• Average force F_avg = Δp / Δt = m v / Δt.

Why B is correct:

• B equals change in momentum divided by contact time, per impulse-momentum theorem.

Why the others are wrong:

• A is impulse (Δp), not force.
• C halves the correct force, possibly confusing with energy.
• D uses undefined M and v², irrelevant to momentum change.

Final answer: B