The left side of the heart creates a pressure of$120mmHg$by exerting a force directly on the blood over an effective area of$15.0c{m}^2$. What force does it exert to accomplish this?

Fluid statics, often known as hydrostatics, is a branch of fluid mechanics that investigates the state of balance of a floating and submerged body, as well as the pressure in a fluid, or imposed by a fluid, on an immersed body.

The pressure is the rate of force applied to the surface per unit area.

It is very important to write all the value in the SI unit.

Basically they gave the value of area and pressure and force is to be calculated

The area A of the blood effective is$15c{m}^2$.

The area A in meter square is$0.0015m^2$.

The pressure P is given as$120mmHg$.

The pressure in Pascal is:

$$\begin{gathered} P=\frac{120\times 1.01\times {10}^5}{760}\text{Pa} \\ =15947.36\text{Pa} \end{gathered}$$

The pressure in Pascal is: $15947.36Pa$.

Since they are equivalent, we can write the above equation as:

$$\begin{gathered} P=\frac{F}{A} \\ F=P\times A \\ =15947.36\times 0.0015 \\ =23.92104\text{N} \end{gathered}$$

Therefore, force exerted is: $23.92N$.