Pressure

The AP sheet prints $P = F_{\perp}/A$, and every word of essential knowledge 8.2.A.1 matters: only the component of the force perpendicular to the surface counts, and it is spread over the area it acts on. A force applied at an angle contributes only its perpendicular part.

EK 8.2.A.2 then states flatly that pressure is a scalar quantity. That is worth holding on to, because the force a fluid exerts on a wall certainly has a direction. Pressure does not: at a point inside a static fluid it pushes with the same magnitude on a surface facing any way, and the direction only appears once you pick a surface for it to act on.

Units: $1\ \text{Pa} = 1\ \text{N/m}^2$, and the AP tables give $1\ \text{atm} = 1.0 \times 10^5\ \text{Pa}$.

Two ideas hang off this one. Pressure in a fluid rises with depth as $P = P_0 + \rho g h$, and the part above the reference pressure $P_0$ is the gauge pressure. The same quantity turns up in Bernoulli's equation as an energy per unit volume, since $1\ \text{Pa}$ is also $1\ \text{J/m}^3$.

The step-by-step depth calculations live in Fluids in AP Physics 1.