Give reason for the following statements:
(a) A liquid inside a dropper comes out only when its rubber bulb is pressed hard.
(b) Two holes are made to empty an oil tin.

Explanation

(a) Liquid is held inside the dropper against the atmospheric pressure. So, when the rubber bulb is pressed hard, pressure on the liquid becomes more than the atmospheric pressure and it comes out.
(b) When only one hole is made in the oil tin and oil comes out of it, the pressure inside the tin becomes less than the atmospheric pressure at some point, and soon, the oil stops flowing out. So, when two holes are made in the tin, air keeps on entering the tin through the other hole and hence, pressure inside the tin is maintained and oil flows out easily and makes the tin empty.