Question

A student uses a spring balance of least count 10g wt and range 500g wt. He records the weight of small iron cube in air, in tap water and in a concentrated solution of common salt in water. If his three readings taken in this order are W_1, W₂ and W_3, he is likely to observe that :
(1) W₁ > W₂ > W₃
(2) W₃ > W₂ > W₁
(3) W₁ > W₃ > W₂
(4) W₂ > W₁ > W₃

Answer 1

When a body is immersed in liquid, it feels an upward force, which is known as buoyant force. The measure of the buoyant force is equal to the weight of the liquid displaced by the body.

When immersed in the liquid, the spring balance will show the net weight reading of the body. So due to buoyant force, the weight of the body in the liquid will be less than the weight of the body in the air. As the density of the salt water is more than the normal water, hence the weight of the displaced salt water will be more than the same volume of the normal tap water, hence the buoyant force will be more when the body will be immersed in the salt water.

The body will have the least weight when immersed in salt water, and most when it is in the air. So we can say, W₁ > W₂ >W₃

Hence, the correct answer is option 1.