# Automotive Pressure Question -- How do you get P = ρgh?

1. Jul 19, 2016

How do you get P = ρgh?

2. Jul 19, 2016

### BvU

Consider a volume of material and make a force balance.
Or look it up in a textbook at high school level

3. Jul 19, 2016

### Mech_Engineer

The equation you've referenced is a simplified fundamental hydrostatics equation, see here: https://en.wikipedia.org/wiki/Hydrostatics#Hydrostatic_pressure

4. Jul 19, 2016

### jack action

$$P = \frac{F}{A} = \frac{mg}{A} = \frac{(\rho V)g}{A} = \rho g \frac{V}{A} = \rho gh$$

5. Jul 22, 2016

### Randy Beikmann

Or, in words, divide the weight of a column of liquid (with constant cross-sectional area A) by the area at the bottom of the column (again, A). Even though this formulation doesn't prove it, the answer is the same whether or not the area is constant, or even the actual shape of the vessel.