Question

Explain how differences in fluid pressure create buoyant force on an object.

Answer 1

Hint: The ability of a fluid – a liquid or a gas – to exert an upward force called the buoyant force on an object immersed in it is termed as buoyancy. A difference in pressure on the object results in the buoyant force.

Complete step by step answer:
A Greek mathematician named Archimedes made a discovery about buoyancy. According to the Archimedes principle, the buoyant force exerted on a body immersed in a fluid is equal to the weight of the fluid displaced by the body. For example, if you place a block of wood in water, it will push water out of the way as it begins to sink – but only until the weight of the water displaced equals the block’s weight. When the weight of water displaced – the buoyant force – becomes equal to the weight of the block, it floats. When an object is immersed in water, the pressure exerted by water horizontally on its sides, cancel out each other. Since, pressure increases with depth, the pressure exerted by water at the bottom of the object is greater than the pressure exerted by water at the top of the object. A difference in pressure creates a force called the buoyant force.

Additional Information:
Buoyant force is obtained by subtracting weight of an object immersed in fluid from the weight of an object in empty space. The answer will be in Newton.

Note:
Buoyant force acts on all sides of an object and not just the bottom. However, as pressure increases with depth, the upward push is greater than the downward push making the net buoyant force upwards.