Pressure in a Liquid (Edexcel GCSE Physics): Revision Note

Pressure & Depth

• When an object is immersed in a liquid, the liquid will exert a pressure, squeezing the object

• This pressure is exerted evenly across the whole surface of the liquid and in all directions

  • The greater the depth of the liquid, the greater the pressure

  • The greater the density of the liquid, the greater the pressure

Understanding Pressure

Higher Tier Only

• In a liquid, the pressure at a point increases with the height of the column of liquid about that point

  • If there is more liquid above that point, then the pressure is more

• This is because the pressure in a liquid is caused by the weight of the liquid pushing against objects immersed in the liquid

  • As the liquid becomes deeper, the amount of liquid (and hence the weight) increases which causes the pressure to increase

• This is why, for example, the pressure increases with the depth of the ocean

  • The pressure on the seabed is far higher than that on the surface of the ocean

• The weight of the liquid also depends on its density

  • A more dense liquid has a greater weight and therefore will exert a higher pressure

Pressure in a column of water increases with depth, shown by the strong and weak jet of water

• In a column of water, the highest pressure would be at the bottom

  • If a hole is made at the bottom of the column, the water will pour out with a large force

  • If a hole was made at the top of the column, the water will pour out with a small force

  • This is because of the difference in pressure in the column caused by the weight of the water