Q:- Why stars twinkle?
Ans:- Do you know the phenomenon of refraction? Refraction is the bending of light as it moves from one medium to another.
Our air has many layers. The light from a star reaches us after refraction as it passes through various layers of air. When the light passes through the earth’s atmosphere, it is made to bend by the layers of the air and it appears as if the stars are twinkle.
Q:- Why a person is pushed back slightly, when he fires a gun?
Ans:- According to Newton’s third law, to every action there is equal and opposite reaction.
As the bullet leaves the nozzle of the gun’s barrel with momentum in a forward direction, as per Newton’s Third law of motion, the ejection on the bullet imparts to the gun an equal momentum in a backward direction. Therefore a person is pushed back slightly, when he fires a gun
Q:- Why ice wrapped in a blanket or saw dust does not melt quickly?
Ans:- There are substances which are conducts heat easily, they are called conductors. But there are substances which do not conduct heat easily; they are called insulators or bad conductors.
Both wood and wool are bad conductors of heat. They do not allow heat rays to react with ice easily. Therefore, ice wrapped in a blanket or saw dust does not melt quickly.
Q:- Why a piece of chalk when immersed in water emits bubbles?
Ans:- Do you know the principle of capillary. The liquid rises in capillary.
Chalk consists of pores forming capillaries. When it is immersed in water, the water begins to rise in the capillaries and the air present there is expelled in the form of bubbles.