3. Why is a train so hard to stop even when it is going
slowly?

For trains the wheels and the rail are both steel, and the steel-steel friction coefficient is around 0.25. So the stopping time and distance will, at best, be three to four times greater than a car.

Explanation:

them things weigh tons and tons. like hundreds of tons. whenever the train is even slightly moving, the force is still so great that it makes it very difficult to stop.

Explanation: my brain knows