Question

A boat is floating in the water. What happens to the buoyant force on the boat if a man gets into this boat?

A. It increases

B. It decreases

C. It remains the same

D. It becomes zero

Answer 1

Hint: Buoyancy is an upward force exerted by a fluid that opposes the weight of a partially or fully immersed object. In a column of fluid, pressure increases with depth as a result of the weight of the fluid in which the object is immersed.

Or you can make a Free body diagram of the body for the given two situations and now compare the forces.

Complete step-by-step solution:

Definition: Buoyancy (also known as the buoyant force) is the force exerted on an object that is wholly or partly immersed in a fluid.

Buoyancy is caused by differences in pressure acting on opposite sides of an object immersed in a static fluid.

Consider the situation when you try to reach the bottom of a swimming pool then deeper you get inside the harder it becomes to go downward further.

This is because:

- When an object is immersed in fluid the pressure on the bottom of an object is greater as compared to the top (since pressure increases with depth).

- The force on the top pushes down and the force on the bottom pushes up (since force is normal to the surface).

- The direction of the net force acting on an object due to the fluid is upward.

We can simply find the Buoyant force ( ${F_{buoyant}}$ ) by subtracting the downward from upward force.

${F_{buoyant}} = {F_{up}} - {F_{down}}$

From the given condition in question as the man steps in steps in the boat the overall weight increases thus the weight of displaced water also increases. And the buoyant force also increases.

Hence, Option A is correct.

Note: There are certain quantities on which Buoyant force depends and certain quantities on which Buoyant force don’t depend.

The factors that affect buoyancy are,

- The density of the fluid

- The volume of the fluid displaced

- The local acceleration due to gravity

- The buoyant force is not affected by

- The mass of the immersed object

- The density of the immersed object