Question

A train is moving along a straight section of track at a constant speed. Which of the following statements about the train is true?

A) If the train is moving at a constant speed, there must be no forces at all acting on the train.
B) If the train is moving at a constant speed, then any forces that might be acting on the train must cancel out.
C) There must be an unbalanced force acting on the train to keep it moving.
D) The train must have a force acting on it larger than the train's inertia in order to keep moving.

Answer 1

If a train is moving at a constant speed, any forces acting on the train must cancel out.

Step-by-step explanation:

When a train is moving along a straight section of track at a constant speed, there must be forces acting on the train.

Statement B is correct: If the train is moving at a constant speed, then any forces that might be acting on the train must cancel out.

For example, if the train is being pulled forward by an engine with a certain force, there must be an opposing force, such as friction between the train's wheels and the track, that cancels out the pulling force.