From a stationary raft weighing 30 kg, a boy weighing 45 kg jumped onto the shore.

From a stationary raft weighing 30 kg, a boy weighing 45 kg jumped onto the shore. At the same time, the raft acquired a speed of 1.5 m / s. What is the speed of the boy.

To find the boy’s speed after a jump, we will use the law of conservation of momentum: | mm * Vm | = | mp * Vp |, whence we express: Vm = mp * Vp / mm.

Variables: mp – weight of the raft (mp = 30 kg); Vp – the speed that the raft has acquired (Vp = 1.5 m / s); mm – boy’s weight (mm = 45 kg).

Let’s calculate: Vm = 30 * 1.5 / 45 = 1 m / s.

Answer: After the jump, the boy acquired a speed of 1 m / s.