A car with a mass of 20 tons, moving at a speed of 0.3 m / s, overtakes a car with a mass of 30 tons

| March 9, 2021 | education

A car with a mass of 20 tons, moving at a speed of 0.3 m / s, overtakes a car with a mass of 30 tons, moving at a speed of 0.2 m / s. What will be the speed of the carriages after the coupler is triggered?

m1 = 20 t = 20,000 kg.

V1 = 0.3 m / s.

m2 = 30 t = 30,000 kg.

V2 = 0.2 m / s.

V -?

Let us write down the law of conservation of momentum during autocoupling of cars in vector form: m1 * V1 + m2 * V2 = (m1 + m2) * V.

Since before and after coupling the cars move in the same direction, then for projections onto the coordinate axis the law of conservation of momentum will take the form: m1 * V1 + m2 * V2 = (m1 + m2) * V.

V = (m1 * V1 + m2 * V2) / (m1 + m2).

V = (20,000 kg * 0.3 m / s + 30,000 kg * 0.2 m / s) / (20,000 kg + 30,000 kg) = 0.24 m / s.

Answer: after coupling, the cars will move together at a speed of V = 0.24 m / s.



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