Question

Choose the correct statements from the following
This question may have multiple correct options
A. A body will sink in a liquid if its weight is equal or greater than the weight of the liquid displaced by it.
B. A body will float in a liquid if its weight is equal to or less than the weight of liquid displaced by it.
C. When a body floats in a liquid, the portion of the body above the surface of the liquid is independent of the density of the body relative to that of the liquid.
D. in still air, a hydrogen filled balloon rises up to a certain height and then stops rising.

Answer 1

Hint: Buoyant force- It is also known as upthrust. It is a force that is exerted by the liquid in an upward direction that opposes the weight of a partially or fully immersed object. It is of three types – positive buoyancy, negative buoyancy, neutral buoyancy. The example of buoyancy can be a ship floating in water.

Complete step by step answer:
According to Archimedes’s principle, if a body floats in the liquid then, the weight of the liquid displaced must be equal to the buoyant force exerted by the liquid. And, a body will sink if the weight of the body will be greater than the weight of the liquid displaced by the body. If the weight of the body is less than the weight of the liquid displaced then, the body will float above the liquid at a higher level.
The balloon will stop rising when it attains a height at which its weight will be equal to the upthrust.As we all know that the density of hydrogen is less than the density of air. As initially, the upthrust due to air is greater than the weight of the hydrogen filled balloon so the balloon rises. But as we go up, the density of air decreases and hence, the upthrust on the balloon also decreases. So, the balloon stops rising.

So, the correct answer is “Option B and D”.

Note: We should have knowledge of the buoyant force or upthrust and should also know how the body applies forces when it is immersed in the liquid. These things are very common in our daily life also, so it creates a clear image and we remember it for a long time. We can analyze hot air balloons and explain how it works as explained above.