CIE A Level Physics复习笔记4.2.5 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

• 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:

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