Hydrostatic Pressure
Any fluid pushes harder the deeper you go, because at greater depth there's more fluid piled up above you, adding its weight. This pressure depends only on how deep you are and what the fluid is — it doesn't matter if the container is wide, narrow, or a weird shape.
P = ρ · g · h
- P — pressure (Pa): the extra push the fluid exerts at that depth
- ρ — density (kg/m³): how much mass is packed into each cubic meter of the fluid
- g — gravitational acceleration (m/s²): how strongly gravity pulls, about ten near Earth's surface
- h — depth (m): how far below the fluid's surface you are
Water has a density of 1000 kilograms per cubic meter. How much pressure does 0.5 meters of water add, using 10 for gravity?
- ρ = 1000 kg/m³
- g = 10 m/s²
- h = 0.5 m
- P = ρ · g · h
- P = 1000 kg/m³ · 10 m/s² · 0.5 m
P = 5000 Pa
Using the same water, what pressure does 1.0 meter of depth add instead of 0.5 meters?
- 10000 Pa
- 5000 Pa
- 2500 Pa
A wide tub and a narrow tube are both filled with water to the same depth. Which has more pressure at the bottom?
- the narrow tube
- the wide tub
- they're the same