Physics - Study Mode

[#631] When a ship enters the sea from a river
Correct Answer

(A) It rises a little

Explanation

Solution: 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.

[#632] The apparent weight of a man in a lift is less the real weight when :
Correct Answer

(D) The lift is going down with an acceleration

Explanation

Solution: 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.

[#633] A balloon filled with hydrogen will
Correct Answer

(B) Reach a particular height and remain floating

Explanation

Solution: 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.

[#634] Which planet has the lowest density?
Correct Answer

(C) Saturn

Explanation

Solution: Saturn is mainly composed of the lightest two gases known, hydrogen and helium. It is the only planet in our solar system whose density is less than water.

[#635] The sensation of weightlessness in a spacecraft in an orbit is due to the
Correct Answer

(B) Acceleration in the orbit which is equal to the acceleration due to gravity outside

Explanation

Solution: The sensation of weightlessness in a spacecraft in an orbit is due to the acceleration in the orbit which is equal to the acceleration due to gravity outside.