Two railway cars weighing 60 tons each move at a speed of 0.8 m / s and catch up with

Two railway cars weighing 60 tons each move at a speed of 0.8 m / s and catch up with the third car weighing 20 tons, which moves at a speed of 1 m / s. Determine the joint speed.

Problem data: m1 (mass of the first car) = m2 (mass of the second car) = 60 t; V1.2 (speed of the first two cars) = 0.8 m / s; m3 (mass of the third car) = 20 t; V3 (speed of the third car) = 1 m / s.

The joint speed of all three cars is determined from the equality: V * (m1 + m2 + m3) = V3 * m3 + V1,2 * (m1 + m2), whence V = (V3 * m3 + V1,2 * 2m1) / (2m1 + m3).

Let’s perform the calculation: V = (20 * 1 + 0.8 * 2 * 60) / (2 * 60 + 20) ≈ 0.83 m / s.

Answer: The combined speed of all three cars is 0.83 m / s.