Concept:At constant temperature, pressure increases when the same amount of air is compressed into a smaller volume because molecular collisions with the walls become more frequent.
Explanation:Pushing the pump handle downward reduces the volume of the trapped air inside the pump.
Since the temperature is constant, the average kinetic energy and speed of the air molecules do not change.
But with less space available, the air molecules travel a shorter distance before hitting the walls, so they collide with the walls more often per second.
More frequent collisions with the walls exert a larger average force per unit area, which increases the air pressure.
This matches Boyle's law: for a fixed mass of gas at constant temperature,
P∝V1.
Answer:C. frequency of collision of the air molecules with the walls of the pump is increased
