I need some help, I can't solve this physics problem.

Question

Answer 1

a) mv = MV + mv/2 by law of conservation of momentum. So, V = mv/(2M).

b) At the top of pendulum we have Mg = MV_min²/l; V_min = √gl

c) MV²/2 = Mgl/2 + 2Mgl; V² = 5gl; V = √5gl; v_min = (2M√gl)/m