Question

When a paper ball is kept near the mouth of a plastic bottle and air is blown through the sides, it will be pushed out because ___.

• A. the air pressure inside the bottle is same as that at its mouth.
• B. the air pressure inside the bottle is more than the pressure at its mouth.
• C. the air pressure inside the bottle is less than that at its mouth.
• D. the pressure is same in the bottle and outside it.

Answer 1

The correct option is B

the air pressure inside the bottle is more than the pressure at its mouth.

The air pressure inside the bottle is more than the pressure at its mouth because the air near the mouth moves faster (pressure of air reduces when it moves fast-Bernoulli's principle). So a paper ball kept near the mouth of a plastic bottle will be pushed out due to this pressure difference.