Explain, with a figure, the cause of the production of upthrust.

Question

Accepted Answer

When an object is immersed in a liquid, the liquid exerts pressure on all its surfaces. Since pressure increases with depth, the pressure (and hence the force) on the lower surface of the object is greater than the pressure on its upper surface. The forces on the left and right (or front and back) side surfaces are equal and opposite, so they cancel out. Subtracting the smaller upward-facing force on the top from the larger upward-facing force on the bottom gives a net resultant force in the upward direction. This net upward force is called upthrust.