Question

A stone is tied to a spring balance. Under which of the following conditions the reading on spring balance will show the least weight?
1. When the stone is completely submerged in the water in a beaker.
2. When the stone is on the surface of water taken in a beaker.
3. When the stone is suspended in air.
4. When the stone is partially submerged in the water in a beaker.

Answer 1

Correct Answer - Option 1 : When the stone is completely submerged in the water in a beaker.

The correct answer is When the stone is completely submerged in the water in a beaker.

• The reading on spring balance will show the least weight when the stone is completely submerged in the water in a beaker.

• Buoyant Force:
  • When a body is immersed partly or wholly in a liquid, a force acts on the body by the liquid in the upward direction.
  • This force is called buoyant force or force of buoyancy or upthrust.
  • It is equal to the weight of the liquid displaced by the body and acts at the centre of gravity of the displaced liquid.
• Archimedes’ Principle:
  • When a body is immersed partly or wholly in a liquid, there is an apparent loss in the weight of the body which is equal to the weight of the liquid displaced by the body.
• Law of Floatation: A body floats in a liquid if
  • The density of the material of the body is less than or equal to the density of the liquid.
  • If the density of the material of the body is equal to the density of the liquid, the body floats fully submerged in liquid in neutral equilibrium.
  • When the body floats in neutral equilibrium, the weight of the body is equal to the weight of displaced liquid.
  • The centre of gravity of the body and centre of gravity of the displaced liquid should be in one vertical line.