A trolley weighing 2 kg, moving at a speed of 3 m / s, collides with a stationary trolley weighing 4 kg and engages with it.

A trolley weighing 2 kg, moving at a speed of 3 m / s, collides with a stationary trolley weighing 4 kg and engages with it. What is the speed of both carts after interaction.

m1 = 2 kg.
V1 = 3 m / s.
m2 = 4 kg.
V -?
Let’s use the law of conservation of momentum: the momentum for a closed system remains unchanged.
Impulse before interaction: m1 * V1.
Impulse after interaction: (m1 + m2) * V.
m1 * V1 = (m1 + m2) * V.
V = m1 * V1 / (m1 + m2).
V = 2 kg * 3 m / s / (2 kg + 4 kg) = 1 m / s.
Answer: the speed of the carts after the collision is V = 1 m / s.