Question

To stop train pull chain please explain

Answer 1

helloo!!

There's a "brake pipe" down the length of the train, coupled through cars. This pipe carries either pressurized air, or vacuum. There are storage tanks on every car which have (already) been charged up off this pipe. When you pull the emergency, you are venting this brake pipe, so the vacuum/pressure suddenly goes away. This is detected by a control valve on the car. The control valve connects the storage tank to a big piston, which pushes brake shoes against wheels.

hope this helps you