Practice MCQ Questions and answers on Physics-GK

When a piece of ice is placed in a beaker containing water, some of its portion remains out of the water level. Since the volume of ice is greater than the water hence after melting the volume of the piece will decrease and the water level will remain the same.

The magnitude of buoyant force depends on the density of the fluid.

A solid needle placed horizontally on the surface of water floats due to surface tension of water.

Purity of a metal can be determined with the help of Archimedes Principle which makes use of the densities and buoyancy of metals. Finding the density of a metal sample can help to determine its purity. It is most commonly used in the checking the purity of gold.

Buoyancy depends on the mass of the liquid displaced.

When a steel ball is placed on the surface of mercury, it does not sink because the density of mercury is greater than that of steel.

The key to why clouds float is that the density of the same volume of cloud material is less than the density of the same amount of dry air. Just as oil floats on water because it is less dense, clouds float on air because the moist air in clouds is less dense than dry air.

When a ship enters a sea from a river ,the ship is elevated or uplifted due to the density of sea water and during the buoyant motion of the ship, as it would gain both potential and kinetic energy when rising in the fluid.

If the lift accelerates downwards with acceleration a, then the apparent weight of the man standing in the lift will be less than the true weight of the man by an amount ma. On the contrary, if the lift accelerates upwards with acceleration, then the apparent weight of the man will be greater than his true weight.

A balloon filled with the hydrogen stops rising after it has attained a certain height in the sky. This is because as height increases, the density of air decreases resulting in a decrease of buoyant force.