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NCERT Solutions Curiosity Chapter 6 .1 Pressure — In-text Questions

Book page 846 Updated on2026-09-05

Q1.
What will happen to the bulge of the balloon if we increase the height of the water column?
Answer

The bulge will get bigger, and it will keep growing each time more water is poured in.

Pour a little more water into one of the pipes of Fig. 6.5 and the balloon at its lower end pushes out further. Repeat it a few times and the bulge increases every time. The reason is that the pressure at the bottom of the pipe depends on the height of the water standing above it: a taller column presses harder on the rubber, and the rubber stretches more.

Height of water column increases
→ pressure at the bottom of the pipe increases
→ balloon bulges more
Q2.
Do you see any relation between the amount of bulge of the rubber balloon and the height of the water column in the pipe?
Answer

Yes — the bulge increases as the height of the water column increases. The two go up together.

Taken with Activity 6.1, this gives the complete rule for the pressure of a liquid in a vessel: it does not depend on the width of the vessel or on how much liquid it holds, but it does depend on the height of the liquid column. The bulge of the balloon is simply a way of seeing that pressure.

Tip: this single result explains the overhead tank, the strong jet from a tap on the ground floor, and the broad base of a dam. Whenever you meet a liquid-pressure question, first ask: how tall is the column above the point in question?
Q3.
Suppose you are living on the second floor of a three-storeyed building and an overhead water tank is placed on the top floor. Will you or your friend on the first floor receive a more powerful stream of tap water? Give reasons.
Answer

Your friend on the first floor gets the more powerful stream.

The tank stands on the top floor, so the height of the water column above a tap is measured downwards from the tank. The first floor is further below the tank than the second floor is, so the column of water above the first-floor tap is taller. A taller column means greater pressure at the tap, and greater pressure means a faster, stronger stream.

Tank on the top floor of a three-storeyed building
Height of water column above second-floor tap = smaller
Height of water column above first-floor tap = larger
→ pressure at first-floor tap is greater → stronger stream on the first floor
Why it happens: nothing about the pipes or the taps has changed — only the vertical distance below the tank. This is also why the topmost floor of a tall building often gets the weakest supply, and why a tank must always be placed above the highest tap it has to serve.
Q4.
Do liquids also exert pressure on the walls of the container?
Answer

Yes. Activity 6.2 is designed to show exactly this, and it does — water shoots out sideways through holes made in the wall of a bottle.

If the water only pushed downwards, it would simply sit in the bottle and nothing would come out of a hole in the side. The fact that it spurts out horizontally proves that the water is pressing outwards on the wall as well.

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