What is upthrust?

Upthrust, also known as buoyant force or buoyancy, is the upward force exerted by a fluid on an object immersed in it. It is a fundamental principle of fluid mechanics, described by Archimedes' principle.

When an object is submerged in a fluid, such as water or air, it displaces some of the fluid volume. The fluid exerts a force on the object in the opposite direction to its weight. This upward force is called upthrust or buoyant force.

The magnitude of the upthrust depends on the volume of fluid displaced by the object and the density of the fluid. The greater the volume of fluid displaced or the higher the density of the fluid, the larger the upthrust. The upthrust is equal to the weight of the fluid displaced by the object.

If the weight of the object is less than the upthrust, the object will experience a net upward force and will float in the fluid. If the weight of the object is greater than the upthrust, the object will sink.

Upthrust is an important concept in understanding the behavior of objects in fluids, such as why ships float, balloons rise in the air, or why objects feel lighter when submerged in water.