A train is traveling west with a force of 820 N, and then the conductor applies the brakes with a force of 500 N. What is the resulting net force on the train?

Answer 1

This problem is poorly presented in so many ways.

trains don't travel with a force, but rather a speed. If the speed is constant, then the net force is zero.

When the conductor applies the brakes with a force of 500N, is that the force of his foot on the control, or the force of the brakes on the wheels, or what?

However, . . .

If the train is accelerating due to a westward force of 820N, and the brakes apply a net eastward force of 500N, then the resultant force acting on the train is clearly 320N westward.

Answer 2

well you need energy only for the train to go.