A railway car weighing 20 tons, moving at a speed of 0.56 m / s, collides with a stationary platform weighing 8 tons

A railway car weighing 20 tons, moving at a speed of 0.56 m / s, collides with a stationary platform weighing 8 tons. Determine their speed after automatic coupling. Disregard the friction on the rails

Given:
m1 = 20 tons = 20,000 kilograms – the mass of a railway carriage;
v1 = 0.56 meters per second – the speed of the railway car;
m2 = 8 tons = 8000 kilograms – the mass of a fixed platform.
It is required to determine v (meter per second) – the speed of the car and the platform after interaction.
According to the condition of the problem, the friction force can be neglected. We also consider the interaction between the car and the platform to be absolutely inelastic. Then, according to the law of conservation of momentum (momentum):
m1 * v1 = (m1 + m2) * v;
v = m1 * v1 / (m1 + m2) = 20,000 * 0.56 / (20,000 + 8,000) = 11,200 / 28,000 = 0.4 meters per second.
Answer: the speed of movement of the carriage and platform will be equal to 0.4 meters per second.

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