Upthrust
Physics: AQA GCSE Higher, topic 5.4.6
Floating and Upthrust
A partially submerged object (an object that’s not fully in a liquid) will experience greater pressure on the bottom surface than on the top surface. This creates a resultant force upwards. We call this force upthrust.
Upthrust = weight of liquid displaced
- The upthrust that acts on an object is equal to the weight of the liquid that has been forced away (displaced) by that object.
Floating
- If the object’s weight is equal to the upthrust, then the forces balance and the object will float in the liquid.
Sinking
- If the object’s weight is greater than the upthrust, then the object will sink.
Test yourself on Upthrust
Upthrust acting on an object in a fluid is equal to what?