How to show pressure exists in liquids

  • Water pressure at a particular point comes from the weight of water above it.

  • Pressure in liquids increases with depth, so the deeper you go the greater the pressure.

  • Pressure exists on surfaces, in air and in liquids. It is calculated with force ÷ area.

This short demonstration will show that water pressure increases with depth

Have a go

Step-by-step guide showing a jug of water, plastic bottle, sticky tape and a pencil.

Click to see a step-by-step slideshow.

1 of 7

How does water pressure work?

The demonstration shows that the water pressure at each hole, depends on the volume of water above it. The bottom hole has a greater amount of water above it, meaning there is greater pressure there.

As the water comes out of the holes, the water level drops, meaning the jets of water from all of the holes slow down.

Air pressure works in a similar way. The air pressure where you are, is determined by the weight of the atmosphere above you.

If you climb a tall mountain, the air pressure decreases because there is less air above you.

Who needs to know about water pressure?

Divers need to be aware of pressure in water. If you dive to the bottom of a swimming pool, your ears may start to hurt. This is due to the extra pressure around you.

Deep sea divers train themselves to go many times deeper and need to know how to cope with this extra pressure.

Submarines can go very deep. They must be designed carefully to handle the enormous water pressure at those depths.

At the bottom of the ocean the pressure is equivalent to an elephant standing on your finger, so submarines have to be very strong indeed!

Where next?

Discover more about this topic from around Bitesize.

What are sound waves?
What are forces?
What is diffusion?