From a stationary boat, weighing 80 kg, a boy jumps to the shore. the boy’s weight is 40 kg, his speed when jumping is 2

From a stationary boat, weighing 80 kg, a boy jumps to the shore. the boy’s weight is 40 kg, his speed when jumping is 2 m / s. what speed did the boat get?

Let us write the law of conservation of momentum for the boat and the boy, taking into account that their speeds were equal to zero before the jump:
m₁ * v₁ + m₂v₂ = 0,
where m₁, v₁ are the mass and speed of the boat,
m₂, v₂ – boy’s mass and speed.
v₁ = -m₂v₂ / m₁ = – (40 kg * 2 m / s) / 80 kg = -1 m / s.
The minus sign for the boat speed is obtained because the boat began to move in the direction opposite to the jump direction.
Answer: Boat speed – 1 m / s,