A force of 300 N is exerted on a surface of 75 m. What is the pressure exerted on the surface?

During the upstroke, the piston moves upwards, increasing the volume inside the cylinder and creating a partial vacuum (lower pressure).

To fill the cylinder with air/fluid, the intake valve (valve K in this diagram) must open. To prevent air/fluid from being drawn back from the outlet, the outlet valve (valve L) must close.

Option C states that valve L is closed while valve K is open, which correctly describes the valve action during the upstroke.

The final answer is $\boxed{\text{C}}$

40)

The force exerted ($F$) is $300 \, N$.
The surface area ($A$) is $75 \, m^2$.

Pressure ($P$) is defined as force per unit area:

The final answer is $\boxed{\text{A}}$