The diagram shows a syringe containing air. The end of the syringe has been sealed. The volume of air is 150cm^3, at a pressure of 100kN/m^2 (100kPa). a). Explain, in terms of the movement of molecules, how the air exerts a pressure on the inside surface of the syringe.

b). A force is now applied to the piston. This compresses the air to 120cm^3. The temperature remains constant. What is the pressure of the air now?