A car with a mass of 20 tons, moving along a horizontal track at a speed of 2 m / s, overtakes

univerkov | February 4, 2021 | education

A car with a mass of 20 tons, moving along a horizontal track at a speed of 2 m / s, overtakes a car with a mass of 20 tons, moving at a speed of 1 m / s, and couples with it. Determine the kinetic energy of the cars after coupling.

m1 = 20 t = 20,000 kg.

V1 = 2 m / s.

m2 = 20,000 kg.

V2 = 1 m / s.

Ek -?

The kinetic energy of the cars after coupling Ek is determined by the formula: Ek = m * V2 / 2, where m is the total mass of the cars, V is the speed of the cars after coupling.

m = m1 + m2.

m = 20,000 kg + 20,000 kg = 40,000 kg.

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

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

V = (20,000 kg * 2 m / s + 20,000 kg * 1 m / s) / (20,000 kg + 20,000 kg) = 1.5 m / s.

Ek = 40,000 kg * (1.5 m / s) 2/2 = 45,000 J.

Answer: the kinetic energy of the cars after coupling is Ek = 45000 J.

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