NCERT Solutions Curiosity Chapter 6 .2 Pressure Exerted by Air — In-text Questions
Book page 866 Updated on2026-09-05
Q1.
You must have experienced that when you blow air into a balloon, it gets inflated. Why?
Answer
Because the air you blow in presses outwards on the inner walls of the balloon, and the rubber stretches under that pressure.
Every breath you blow adds more air into the same small space. The air inside pushes on the rubber from within; the atmosphere outside pushes back. As long as the inside pressure is greater, the rubber is stretched and the balloon grows. It stops growing when the stretched rubber is taut enough to balance the extra pressure inside.
Q2.
Can we say that air exerts pressure in all directions?
Answer
Yes — and the balloon itself is the proof, because it swells in every direction, not just upwards or sideways.
If the air inside pushed only downwards, the balloon would sag at the bottom and stay flat elsewhere. Instead it rounds out equally all over, which tells us the air inside is pressing equally on every part of the wall. The same is true of the air outside: it presses on the top, the sides and the underside of every object around us.
Did you know? Liquids behave the same way — Activity 6.2 showed water pressing sideways on the bottle wall. Both liquids and gases exert pressure on the walls of a container, in all directions.
Q3.
What happens when an inflated balloon is kept without closing its mouth? Why does the air escape from the balloon?
Answer
The air rushes out and the balloon collapses. It escapes because the pressure of the air inside the balloon is greater than the atmospheric pressure outside.
The stretched rubber squeezes the air within, so the air inside is at a higher pressure than the air in the room. Air always moves from a region of higher pressure to a region of lower pressure. The open mouth gives it a path, so it flows out until the pressures inside and outside are equal — by which time the balloon has shrunk back to its original size.
Why this matters later: this is the seed of the whole idea of wind. A punctured bicycle tube empties for exactly the same reason, and Activity 6.5 turns the observation into a rule: air moves from a region of high pressure to a region of low pressure.