Answer:
The air is contained at a high pressure in the tube. When it escapes from a small orifice, it suddenly expands. A large amount of its heat is absorbed in the process of expansion resulting in considerable fall in its temperature. This is why the escaping air feels cold.
When Sam presses the brake lever, a pair of rubber shoes clamps onto the metal inner rim of the front and back wheels. As the brake shoes rub against the wheels, friction is caused and the kinetic energy possessed by the vehicle is converted into heat which slows down the vehicle.
