Question

same force small mass; large acceleration large mass; small acceleration force = mass x acceleration explanation: 1st law 2nd law 3rd law explanation: 1st law 2nd law 3rd law motion of train apparent force on passengers

Explanation:

First - top part:

The equation $F = ma$ (Force = mass x acceleration) is Newton's second - law. It shows that for the same force, a smaller mass has a larger acceleration and a larger mass has a smaller acceleration.

Second - bottom part:

When the train moves and stops, the passengers experience a force. This is an example of Newton's third - law. The train exerts a force on the passengers, and the passengers exert an equal and opposite reaction force. The motion of the passengers relative to the train's change in motion is due to the action - reaction pair of forces.

Answer:

Top explanation: Newton's second - law states that force is directly proportional to mass and acceleration ($F = ma$), so for a given force, mass and acceleration are inversely related.
Bottom explanation: Newton's third - law is demonstrated as the train's motion change causes a force on passengers and there is an equal and opposite reaction involved in their relative motion.