Question

An object is thrown into a deep lake. As it sinks deeper and deeper into the water, does the buoyant force upon it increase or decrease?

• A. Increase
• B. Remains unchanged
• C. Decreases
• D. First increase then stabilizes

Answer 1

Answer: (B)

Remains unchanged

Objects weigh more in air than in water. When the stone sinks, the weight of the stone appears to weigh less. The missing weight is equal to the weight of the water displaced. This weight is equal to the buoyant force.
That is, Loss in weight of body = Weight of water (liquid) displaced by the body = Buoyant force or upthrust exerted by water (any liquid) on the body.
Once the stone is fully submerged, the buoyant force will remain unchanged because the volume of water that it displaces will remain unchanged.