Final answer:
The upthrust of a fluid, also known as buoyant force, is the upward force exerted on an object immersed in a fluid. It can be demonstrated by observing the floating of objects in a fluid through a simple experiment.
Step-by-step explanation:
The upthrust of a fluid, also known as buoyant force, is the upward force exerted on an object immersed in a fluid. It occurs because pressure increases with depth in a fluid. When an object is submerged in a fluid, the pressure at the bottom is greater than the pressure at the top, resulting in a net upward force.
An experiment to demonstrate the existence of upthrust can be performed by using a simple setup. Take a container filled with water and place a solid object in it, such as a wooden block or a metal ball. Observe that when the object is released, it rises to the surface of the water. This happens because the buoyant force acting upward is greater than the weight of the object, causing it to float.
In conclusion, the upthrust of a fluid is a result of pressure differences within the fluid. It is responsible for the floating of objects in a fluid and can be demonstrated through the use of a simple experiment.