NCERT Solutions for Class 8th Science Chapter 6 .1 Pressure — In-text Questions
Book page 836 Updated on2026-09-19
Q1.
You must have seen overhead water tanks (Fig. 6.4) in your locality, or on the rooftops of houses used for water supply. Why are these tanks always placed at a height?Fig. 6.4, page 83 — redrawn sketch: an overhead water tank standing on a tall steel tower, with the supply pipe running down to the ground.
Answer
Because the pressure a liquid exerts depends on the height of its column, and it is that pressure which drives water out of the taps.
Water in the tank is connected to every tap in the house by pipes. The taller the column of water standing above a tap, the greater the pressure at that tap. Placing the tank on the roof makes this column as tall as possible, so the water leaves the taps in a strong stream and can also reach taps on the upper floors.
Why it happens: Activity 6.1 shows that a taller water column bulges the balloon more, and that widening the pipe changes nothing. So it is height alone — not the size of the tank or the amount of water in it — that sets the pressure at the outlet.
Q2.
Do liquids also exert pressure?
Answer
Yes. A liquid presses on the bottom of its container, on the walls of the container, and in fact in all directions.
Activity 6.1 makes the pressure at the bottom visible: the balloon tied to the lower end of a water-filled pipe bulges outwards, and it bulges more when the water column is made taller. Activity 6.2 shows the sideways pressure: water spurts out of holes made in the side wall of a bottle. Between them, the two activities establish that a liquid exerts pressure everywhere it touches its container.
Check it yourself: the base of a dam is built much broader than its top for exactly this reason. The horizontal pressure of the stored water is largest near the bottom, and the broad base is needed to withstand it (Fig. 6.8).