Question

A body measures 5N in air and 2N when put in water. The buoyant force is :-
A) 2 N
B) 9 N
C) 3 N
D) None of these

Answer 1

According to this question, we need to measure the buoyant force acting on a body that measures 5N in air and 2N when put in water. Buoyant force is the upward force a fluid exerts on an object. To solve this question, we need to remember the concept of buoyant force = weight lost by the body = weight in air - weight in water.

Complete Step By Step Answer:
The upward force exerted by fluids (liquid and gas) on objects when they are immersed in them is called buoyant force and the phenomenon is called buoyancy.
Now to keep the object immersed we have to apply external force from upward direction to overcome buoyant force.
Archimedes' principle states that the upward buoyant force that is exerted on a body immersed in a fluid, whether fully or partially, is equal to the weight of the fluid that the body displaces. Archimedes' principle is a law of physics fundamental to fluid mechanics. It was formulated by Archimedes of Syracuse.
According to Archimedes principle,
buoyant force = weight lost by the body = weight in air - weight in water =
$5N - 2N = 3N$
Hence, the final answer is C) 3 N.

Additional Information:
The Archimedes principle is a very useful and versatile tool. It can be useful in measuring the volume of irregular objects, such as gold crowns, as well as explaining the behaviours of any object placed in any fluid. Archimedes' principle describes how ships float, submarines dive, hot air balloons fly, and many others examples, according to Science Clarified. The Archimedes principle is also used in a large variety of scientific research subjects including medical, engineering, entomology, engineering, and geology.

Note:
It is important to note that the buoyant force does not act in any random direction. The buoyant force on a body due to a liquid acts in the direction at the centre of buoyancy and in the opposite direction of weight of the body.