A trolley with a mass of 3 kg, moving at a speed of 4 m / s, collides with a stationary trolley

A trolley with a mass of 3 kg, moving at a speed of 4 m / s, collides with a stationary trolley with a mass of 5 kg and engages with it. What is the speed of both trolleys after interaction?

According to the law of conservation of momentum, the following expression is true:
m1V1 = (m1 + m2) U1, where m1 is the mass of the first cart (m1 = 3 kg), m2 is the mass of the second cart (m2 = 5 kg); V1 is the initial speed of the first carriage (V1 = 4 m / s), U1 is the speed of the carts after interaction (m / s).
Let’s calculate the speed of the carts after interaction:
U1 = m1V1 / (m1 + m2) = 3 * 4 / (3 + 5) = 12/8 = 1.5 m / s.
Answer: The speed of the carts after interaction will be equal to 1.5 m / s.