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NCERT Solutions Curiosity Chapter 6 .2 Pressure Exerted by Air · 6.3 Formation of Wind — In-text Questions

Book page 876 Updated on2026-09-05

Q1.
Do you know how large the atmospheric pressure is?
Answer

It is very large. Over an area of 15 cm × 15 cm, the atmospheric air column pushes with a force of about 2250 N — nearly the force of gravity on an object of mass 225 kg.

Work out what that means for the area itself:

Area = 15 cm × 15 cm = 0.15 m × 0.15 m = 0.0225 m2
Pressure = Force / Area = 2250 N ÷ 0.0225 m2
= 100000 N/m2 = 1 × 105 Pa

So every square metre of ground, roof or skin carries about a hundred thousand newtons of atmospheric push. We survive it because the pressure inside our bodies — produced by the movement of fluids and gases in our tissues and organs — is also equal to the atmospheric pressure, and it balances the pressure from outside.

Tip: in weather work this pressure is usually written in the practical units given in A step further: 1 millibar (mb) = 1 hectopascal (hPa) = 100 Pa, so 100000 Pa is about 1000 mb — which is why the isobars in Fig. 6.19 read 994 mb, 996 mb, 998 mb and 1008 mb.
Q2.
You must have seen that when an inflated balloon is kept without closing its mouth, the air from the balloon escapes. Recall that when there is a puncture in the bicycle tube, the air escapes and the tube collapses. In both of these cases, does air move from a high pressure region to a low pressure region?
Answer

Yes. In both cases the air inside is at a higher pressure than the air outside, and it flows out until the two pressures are equal.

In the balloon, the stretched rubber squeezes the air within. In the bicycle tube, the pump has forced a large amount of air into a small volume. Both hold air at a pressure well above atmospheric. Open the balloon's mouth or puncture the tube, and you give that high-pressure air a path to the low-pressure air outside — so out it goes, and the balloon or tube collapses.

Why it matters: this is the rule that produces wind. Air anywhere on the Earth behaves the same way — it moves from a region of high air pressure towards a region of low air pressure. Activity 6.5 demonstrates it in a controlled way, with two balloons joined by a straw.
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