Explain the operation of a bicycle pump, detailing what happens when the handle is drawn out and when it is pushed in.

Here's what happens when the pump is operated:

a) Explain what happens when the pump is drawn out.
When the pump handle is drawn out (pulled to the right), the piston moves to the right. This increases the volume inside the barrel to the left of the leather washer, causing the pressure inside to drop below atmospheric pressure. The external atmospheric pressure then pushes air from the outside into the barrel, past the leather washer, filling the space behind the piston.

b) Explain what happens when the pump is drawn in.
When the pump handle is drawn in (pushed to the left), the piston moves to the left. This compresses the air inside the barrel. The leather washer expands and seals tightly against the barrel walls, preventing air from escaping back past the piston. As the pressure of the compressed air increases, it forces open the valve of the bicycle tyre, and the air is pushed into the tyre.