NCERT Solutions Curiosity Chapter 6 .1 Pressure — Activity 6.1: Let us try and find out
Book page 836 Updated on2026-09-05
Q1.
Do both balloons bulge? Do they bulge to the same extent?
Answer
Yes, both balloons bulge — and they bulge to exactly the same extent, even though one pipe is broad and the other narrow.
Both pipes are about 25 cm long and are filled with water to the same level, roughly half way. The balloon at the lower end of each pipe pushes out, and the two bulges look alike. This is surprising at first, because the broad pipe holds much more water than the narrow one, and therefore a much greater weight of water.
Equal heights of water column produce the same bulge in both balloons, although the broad pipe holds far more water.
Q2.
What can you infer from this activity?
Answer
That the bulge is produced by the pressure of the water column, and that this pressure depends on the height of the column, not on the weight of water above the balloon.
Reason it through. The two pipes have different diameters, so they hold different weights of water. If the weight of water were responsible for the bulge, the broad pipe's balloon would have bulged much more. It does not — the two bulges are equal. So weight cannot be the cause. What is the same in the two pipes is the height of the water column, and that is what the bulge follows.
Why it happens: the extra water in the broad pipe also rests on a proportionately larger area of the pipe's cross-section. Force and area grow together, so force divided by area — the pressure — stays the same. This is why equal water column heights produce equal bulges despite different diameters.