A boy weighing 45 kg dives from a boat weighing 250 kg, moving at a speed of 0.7 m / s, moving in a horizontal direction.

A boy weighing 45 kg dives from a boat weighing 250 kg, moving at a speed of 0.7 m / s, moving in a horizontal direction. What will the boat speed after the boy’s jump if he jumps from the stern at a speed of 5.5 m / s?

According to the law of conservation of momentum, mv (general) = m1v1 + m2v2. It remains to substitute everything into the formula.
(250kg + 45kg) * 0.7m / s = 250kg * v1 + 45kg * 5.5m / s
v1 = 0.164