In: Physics
1. All train cars in this problem are identical and have masses of 45,000 kg each. Three cars, coupled together, are rolling east at 2.4 m/s. A fourth car, traveling west at 3.4 m/s collides with the three and couples to make a four car unit. A moment later, the train cars contact a car that was at rest on the tracks, and it couples to make a five car train.
a) What is the speed of the five car train?
b) How much (constant) force will be necessary to bring the train to a stop in 250 m? Neglect friction.
This is a question based on collision. In this type of questions, if no external force is present we can apply conservation of linear momentum. And we can apply Newton's second law to get the relationship between force and acceleration. As given in the question force is constant. Thus retardation provided by the force to the train would also be constant.