If a train is traveling eastward with a constant velocity of 15 m/s, what is the net external force action on it? there is not enough information, so it cannot be solved. there is no net force acting on the train. the force from the engines

There is no net force acting on the train.

Explanation:

The net force equals mass times acceleration:

∑F = ma

The train moves at constant velocity, so its acceleration is 0.  Therefore, the net force is 0.

If a train is travelling eastward with a constant velocity of 15 m/s, there is no net force acting on the train.

Option B

Explanation:

According to Newton 2nd law, the external force is proportionate to the rates of change of momentum which states that force will be indirectly proportional to the rates of variation in velocity. So, as the velocity is constant for the train, the rate of variation in velocity or the acceleration will be zero. Thus the total external forces acting on the train will be zero. But the train will be moving continuously due to the energy obtained from the engine.

at positions a, g kinetic energy is maximum.

at position d, potential energy is maximum.

i don't know that i agree with that but what's the question ?