Key Stage 3
Meaning
Upthrust is a force that acts upwards in a fluid due to the fluid being displaced.
About Upthrust
- Upthrust is a force so it is measured in Newtons.
- The force of upthrust is equal to the weight of fluid that has been displaced.
- An object in the water experiences as lot of upthrust because water is dense.
- Upthrust is weak in the air because the air is not very dense. For most objects in air upthrust can be ignored because it is so small.
- Upthrust is caused by the pressure in a fluid. Pressure increases with depth so the bottom of an object will experience more pressure than the top. This difference in pressure results in more force on the bottom than the top, known as upthrust.
Examples
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| A boat floats on the water because the weight is balanced by the upthrust. | A submarine can change the amount of upthrust in order to rise or sink in the water. |