CIE AS Physics (9702) exams from 2022

Revision Notes

4.2.5 Archimedes Principle

Archimedes' Principle

  • Archimedes’ principle states that an object submerged in a fluid at rest has an upward buoyancy force (upthrust) equal to the weight of the fluid displaced by the object
  • The object sinks until the weight of the fluid displaced is equal to its own weight
  • Therefore the object floats when the magnitude of the upthrust equals the weight of the object
  • The magnitude of upthrust can be calculated by:

Upthrust equation, downloadable AS & A Level Physics revision notes

Upthrust equation

 

  • Since m = ρV, upthrust is equal to F = mg which is the weight of the fluid displaced by the object
  • Archimedes’ Principle explains how ships float:

Upthrust on a boat, downloadable AS & A Level Physics revision notes

Boats float because they displace an amount of water that is equal to their weight

 

Worked example

Worked example - Archimedes' principle iceberg (1), downloadable AS & A Level Physics revision notes

Worked example - Archimedes' principle iceberg (2), downloadable AS & A Level Physics revision notes

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