A stone is tied to a spring balance. Under which of the following conditions the reading on spring balance will show the least weight?
- AOption (a)
When the stone is completely submerged in the water in a beaker.
- BOption (b)
When the stone is on the surface of water taken in a beaker.
- COption (c)
When the stone is suspended in air.
- DOption (d)
When the stone is partially submerged in the water in a beaker.
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Correct answer
When the stone is completely submerged in the water in a beaker.
Why this answer is correct
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.
Important Points
- 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 the centre of gravity of the displaced liquid should be in one vertical line.


















