Question

In the set up shown the weight of the body was measured in air and in water. The reading of mark X in the spring balance would be :



(1) 36g wt
(2) 30g wt
(3) 24g wt
(4) 6g wt

Answer 1

When a body is immersed in a liquid, it feels an upward force, which is known as the buoyant force. The measure of the buoyant force is equal to the weight of the liquid displaced by the body. As we can see from the given figure, the volume of the liquid displaced is 6 mL, so the weight of the water displaced it 6 g wt. (Density of the water = 1 g/mL)

When the body is immersed in water, the spring balance will show the net weight of the body.

Net weight of the body in liquid = Actual weight $-$ Buoyant force = 30 g wt $-$ 6 g wt. = 24 g wt.

Hence, the correct answer is option 3.