Answer:
Newton's 3rd law of motion states that:
"When an object A exerts a force on an object B (action force), then object B exerts an equal and opposite force on object A (reaction force)"
In this problem, we can identify:
- The rocket as object A
- The gas expelled by the rocket as object B
Therefore, Newton's 3rd law of motion applied to this situation is:
- The rocket exerts a force (in the backward direction) on the gas, which is expelled by the rocket
- As a result, the gas exerts a reaction force (in the forward direction) on the rocket, and this force is what explains why the rocket moves forward.
