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

where is the circuit diagram ?

answer: the metamorphic rocks are formed when they are exposed to high pressure and high temperatures. this happens when one of the earth's plates comes in contact with the other plate by traveling in opposite directions, straight into each other or slipping under one another. the friction that is caused by this activity results in   melting of rocks and when it cools they are known as metamorphic rocks. this process needs a controlled amount of pressure and temperature otherwise it may turn into magma.