Afreight car moves along a frictionless level railroad track at constant speed. the car is open on top. a large load of coal is suddenly dumped into the car. what happens to the velocity of the car?

Velocity of the car decreases.

Explanation:

We can understand the situation if we apply the conservation of energy principle to the situation

Let the initial mass of the freight be

Initial velocity of the freight be

Thus the initial Kinetic energy of the freight will be

When a Coal Block of mass M falls into the freight it's energy will become

Equating both the energies we get final velocity as

As we see that is less than 1 we can infer that velocity decreases.

like poles repel so keep pushing north to north and repels funny to see this