How does Newton's third law apply to roller coasters?
i guess there is another one but kind of simple
As the roller coaster moves forward. The motion is in the forward direction, so the opposing force( the air) is moving exactly the opposite direction. this is another example which is simple.
Yet please correct me because i can always be wrong
The drag is opposing the aceleration of the engine (going up) or the gravity accel. (moving down).
But I suggest you to be more specific. For example, there is always the normal force (tires - rails), else the roller coaster and the cars would trespass each other, and this is a trivial consideration.