# Calculating Force Acting On Door Due To Water Pressure

#### jot_dain

Hello all

I was hoping someone could help with the following force/pressure problem.

I am trying to find the force due to water pressure acting on the green door under the tube as shown below:- I work out the force as:-

Force = Density of fluid * gravity * Area * Height below water surface

Density of fluid = 1000
Gravity = 9.8
Area * Height below water surface = 0.2827
Height below water surface = 20

Force = 1000 * 9.8 * 0.2827 * 20 = 55409.2 Newtons

To be honest i am not sure if i should be taking the height below the water surface as 20 or 20 + 11.2 i.e. 31.2m.

I was hoping someone could help shed some light.

Thank you.

#### studiot

Hello all

To be honest i am not sure if i should be taking the height below the water surface as 20 or 20 + 11.2 i.e. 31.2m.

I was hoping someone could help shed some light.

Thank you.
WellI assume the tank is full so the head at the green door (are you a Shaking Stevens fan?) must include the 11.2 m wheere there is a free water surface at atmospheric pressure.

The green door is halfway along the pipe so its depression below the bottom of the tank is half of 20 metres or 10 metres.
So the total head is 11.2 + 10