Upthrust Flashcards

All 8 cards in this deck

What is upthrust?

The upward force that a fluid exerts on an object immersed in it.

Why does a fluid exert an upthrust on a submerged object?

The pressure at the bottom of the object is greater than at the top, so the upward force on the bottom is greater than the downward force on the top.

What is the upthrust on an object equal to?

The weight of the fluid displaced by the object.

What condition on upthrust and weight makes an object float?

It floats if the upthrust can equal its weight; it sinks if its weight is greater than the maximum upthrust.

How do densities tell you whether an object will float in a liquid?

It floats if its density is less than the density of the liquid, and sinks if its density is greater.

True or false? Objects in air experience no upthrust.

False. Air is a fluid, so it gives an upthrust — it is just very small because air has a low density.

What happens to the upthrust on an object as it is lowered further into water, while still only partly immersed?

The upthrust increases, because more water is displaced.

True or false? Once an object is completely submerged, lowering it deeper into the same liquid increases the upthrust on it.

False. The volume of liquid displaced no longer changes, so the upthrust stays the same.