Chapter 11, Problem 73PQ

Three runaway train cars are moving on a frictionless, horizontal track in a railroad yard as shown in Figure P11.73. The first car, with mass m₁ = 1.50 × 10³ kg, is moving to the right with speed v₁ = 10.0 m /s; the second car, with mass m₂ = 2.50 × 10³ kg, is moving to the left with speed v₂ = 5.00 m/s, and the third car, with mass m₃ = 1.20 × 10³ kg, is moving to the left with speed v₃ = 8.00 m /s. The three railroad cars collide at the same instant and couple, forming a train of three cars.

1. a. What is the final velocity of the train cars immediately after the collision?
2. b. Would the answer to part (a) change if the three cars did not collide at the same instant? Explain.

FIGURE P11.73