Forces and Motion

Getting to the bottom of Archimedes’ principle

Stories from Physics for 11-14 14-16 IOP RESOURCES

A special case of Archimedes’ principle occurs when an object rests at the bottom of a tank of liquid. For example, when a submarine rests on the floor of the ocean, it cannot rise simply by blowing water out of its buoyancy tanks as it has no water underneath it to provide an upward force, only water pressing down from above. Hence, definitions of Archimedes’ principle that emphasise the effect of a net force due to a difference in pressure are seen as seen as exemplary, rather than definitions that simply link buoyancy to the weight of water displaced.



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