Pressure, Winds, Storms, and Cyclones | Class 8 Science Notes
By ConceptScroll Team · Published on 17 July 2026 · 5 min read
Pressure, Winds, Storms, and Cyclones – this guide gives you a concise, exam-ready overview of Pressure, Winds, Storms, and Cyclones from Class 8 Science, written by ConceptScroll editors and reviewed against the latest NCERT textbook.
Pressure Exerted by Liquids
Liquids exert pressure on the surfaces in contact with them, including the bottom and sides of their containers. This pressure arises due to the weight of the liquid column above the point of measurement and acts equally in all directions.
An activity with two transparent pipes of different diameters but the same height filled with water demonstrates that the pressure at the bottom depends on the height of the water column, not on the volume or weight of water. Both balloons attached to the pipes bulge equally, indicating equal pressure despite different water volumes.
Increasing the height of the water column increases the pressure at the bottom, causing the balloon to bulge more. This principle explains why overhead water tanks are placed at a height—to increase water pressure at taps, ensuring a strong water stream.
Liquids also exert pressure sideways on the walls of containers, which can be observed by making holes near the bottom of a water-filled bottle. Water squirts out horizontally, showing that pressure acts in all directions.
The pressure exerted by liquids is crucial in engineering structures like dams. The base of a dam is broader than the top to withstand the large horizontal water pressure near the bottom caused by the height of the water. This horizontal pressure increases with depth, requiring stronger support at the base.
In summary, liquid pressure depends on the height of the liquid column and acts in all directions, influencing natural phenomena and human-made structures.
📊 Diagram: Fig. 6.5 shows two pipes of different diameters with balloons attached, filled with water to the same height, demonstrating equal pressure. Fig. 6.6 illustrates increased balloon bulge with increased water height. Fig. 6.7 depicts a bottle with holes near the bottom, showing water squirting due to lateral pressure. Fig. 6.8 shows a dam with a broad base to withstand water pressure.
🧪 Activity: Activity 6.2 involves making holes near the bottom of a water-filled bottle and observing water squirting out, demonstrating that liquids exert pressure sideways as well as downward.
🔗 Connection: This section builds on the concept of pressure to introduce atmospheric pressure and how gases exert pressure.
Frequently asked questions
1. Choose the correct statement. (i) Look at Fig. 6.21 carefully. Vessel R is filled with water. When pouring of water is stopped, the level of water will be (a) the highest in vessel P (b) the highest in vessel Q (c) the highest in vessel R (d) equal in all three vessels (ii) A rubber sucker (M) is pressed on a flat smooth surface and an identical sucker (N) is pressed on a rough surface: (a) Both M and N will stick to their surfaces. (b) Both M and N will not stick to their surfaces. (c) M will stick but N will not stick. (d) M will not stick but N will stick. (iii) A water tank is placed on the roof of a building at a height 'H'. To get water with more pressure on the ground floor, one has to (a) increase the height 'H' at which the tank is placed. (b) decrease the height 'H' at which the tank is placed. (c) replace the tank with another tank of the same height that can hold more water. (d) replace the tank with another tank of the same height that can hold less water. (iv) Two vessels, A and B contain water up to the same level as shown in Fig. 6.22. PA and PB is the pressure at the bottom of the vessels. FA and FB is the force exerted by the water at the bottom of the vessels A and B. (a) PA = PB, FA = FB (b) PA = PB, FA < FB (c) PA < PB, FA = FB (d) PA > PB, FA > FB
1.(i) (d) equal in all three vessels. Explanation: The water level will be equal in all connected vessels due to the principle of communicating vessels.
(ii) (c) M will stick but N will not stick. Explanation: A rubber sucker sticks to a smooth surface because of air pressure difference; on a rough surface, air can enter, so it won't stick.
(iii) (a) increase the height 'H' at which the tank is placed. Explanation: Pressure due to water depends on height of water column, so increasing height i
2. State whether the following statements are True [T] or False [F]. (i) Air flows from a region of higher pressure to a region of lower pressure. (ii) Liquids exert pressure only at the bottom of a container. (iii) Weather is stormy at the eye of a cyclone. (iv) During a thunderstorm, it is safer to be in a car.
(i) True. Air moves from high to low pressure causing wind. (ii) False. Liquids exert pressure in all directions, not only at the bottom. (iii) False. The eye of a cyclone is calm with low pressure. (iv) True. Being inside a car is safer during thunderstorms as it acts like a Faraday cage.
3. Fig. 6.23a shows a boy lying horizontally, and Fig. 6.23b shows the boy standing vertically on a loose sand bed. In which case does the boy sink more in sand? Give reasons.
The boy sinks more when standing vertically (Fig. 6.23b). Reason: Pressure is force per unit area. When standing, the boy's weight is concentrated on a smaller area (feet), increasing pressure on sand, causing him to sink more. When lying horizontally, the weight is distributed over a larger area, reducing pressure and sinking.
4. An elephant stands on four feet. If the area covered by one foot is 0.25 m², calculate the pressure exerted by the elephant on the ground if its weight is 20000 N.
Given: Weight, W = 20000 N Area per foot, A_foot = 0.25 m² Number of feet = 4 Total area, A_total = 4 × 0.25 = 1 m²
Pressure, P = Force / Area = W / A_total = 20000 N / 1 m² = 20000 Pa
Therefore, the pressure exerted by the elephant on the ground is 20000 pascals (Pa).
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