AQA GCSE Pressure at the surface of the fluid

AQA GCSE Pressure at the surface of the fluid

Pressure at the surface of the fluid

Pressure is defined as the amount of force per unit area.

Formula triangle for pressure using pressure= force/area

Pressure at the surface of a fluid

Fluids include both liquids and gases

At the surface of a fluid the pressure causes a force at 90 degrees to the surface, or normal to the surface. 

Pressure at the surface of a fluid

In this case you can see for the submerged ball the force arrows all act at 90 degrees to the surface of the fluid.

In the example below of a gas in a container. The force arrows are at 90 degrees or normal to the container walls. So, as the gas particles collide with the walls a force is caused, which represents the gas pressure. The walls of the container will meet the surface of the fluid (gas).
Gas pressure and force diagram 

Practice questions

1.Use the image below to answer the following question.

pressure at the surface of a fluid

The total force at the surface of the fluid is 500N and this force occurs along a total surface area of 0.4m2. Calculate the pressure.

2. Using the image below to answer the following question.

balloon suspended in air to show pressure at the surface of the fluid

Add force arrows to the diagram above to show the pressure acting at the surface of the balloon.

Remember that both the air outside of the balloon and the air in the balloon act as a fluid. 

3. Use the image below to answer the following question

pressure acting at the surface of a fluid
Identify all the possible places in the diagram above where force arrows should be drawn to represent the pressure acting at the surface of a fluid.
Accordion Content
Accordion Content
Accordion Content