A car weighing 20 tons moves at a speed of 1.5 m / s and meets a platform weighing 10 tons

A car weighing 20 tons moves at a speed of 1.5 m / s and meets a platform weighing 10 tons standing in the way. At what speed will they move after the coupler is triggered?

Initial data: m1 (wagon weight) = 20 t; V1 (speed of the car before the automatic coupling) = 1.5 m / s; V2 (platform speed to automatic coupling) = 0 m / s; m2 (platform weight) = 10 t.

Since the platform before the automatic coupling was motionless, the equality (the law of conservation of momentum) is true: m1 * V1 = (m1 + m2) * V1,2, whence V1,2 = m1 * V1 / (m1 + m2).

Let’s calculate: V1.2 = 20 * 1.5 / (20 + 10) = 30/30 = 1 m / s.

Answer: After the automatic coupler is triggered, the car with the platform will move at a speed of 1 m / s.