3. Consider a locomotive and the rest of a freight train to be a single object. Suppose the locomotive is pulling the train up a hill. Describe the action and reaction forces that cause the locomotive to move up the hill, such as the reaction force and gravity.

This question has been posted before put the answers were not correct.

Action - Pulling up the train.

Reaction - Friction on the locomotive

Explanation:

Locomotive is pulling the train upwards,

Which is the action force applied by the locomotive,

As a reaction locomotive will be pulled by the train which is the reaction of pulling

Now, considering it as a action on locomotive, friction force will act on it as a reaction upwards which will result to move it upwards.

For train action is pulling up by locomotive and reaction will be friction acting on it downwards.