NCERT Solutions for Class 8 Science Chapter 6 – Pressure, Winds, Storms, and Cyclones

The NCERT Solutions for Class VIII Science, Chapter 6 'Pressure, Winds & Storms and Cyclones' provides insight into how atmospheric pressure causes wind to flow in one direction to the next (i.e., wind blows from an area of higher to lower atmospheric pressure) as well as gives readers a greater understanding of natural disasters such as cyclones and storms, and their relationship with atmospheric conditions, etc. 

Most importantly, it creates further knowledge for students, giving them a better understanding of how these particular weather events can create dangers to themselves and other people and therefore motivates students to prepare for those types of emergencies to keep themselves and those around them safe.

1.0NCERT Solutions for Class 8 Science Chapter 6 PDF Download

This section provides students with convenient access to the downloadable PDF of Pressure, Winds, Storms, and Cyclones Class 8 solutions for effective revision.

The NCERT Solutions for Class 8 Science Chapter 6 PDF are meticulously prepared by ALLEN’s expert faculty members, ensuring accuracy, clarity, and full syllabus coverage.

2.0NCERT Questions with Solutions Class 8 Science Chapter 6 Detailed Solutions

1. Choose the correct statement:

(i) Look at the Figure 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

Answer (d) equal in all three vessels

Since vessels P, Q, and R are connected and open to the same atmospheric pressure at the top, the liquid (water) will reach the same horizontal level in all three vessels, regardless of their shape or size.

(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) Neither M nor N will stick to their surfaces
(c) M will stick, but N will not stick
(d) M will not stick, but N will stick

Answer
(c) M will stick, but N will not stick

A rubber sucker works because when it is pressed onto a surface, the air between the sucker and the surface is forced out, creating a partial vacuum (lower pressure) inside the sucker. The atmospheric pressure pushing on the outside of the sucker is then greater than the pressure inside, holding the sucker firmly in place.

• On a flat smooth surface (M), a good seal is formed, allowing the partial vacuum to be maintained.
• On a rough surface (N), air can easily leak back into the space under the sucker through the gaps and irregularities, preventing a sufficient pressure difference (partial vacuum) from being created, so it will not 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.

Answer
(a) increase the height ‘H’ at which the tank is placed.

• Since pressure (P) increases with height (h or H), increasing the height ‘H’ of the water tank above the ground floor will directly increase the water pressure at the ground floor.
• The pressure does not depend on the volume of water the tank can hold (options c and d), only on the vertical height of the water head.

(iv) Two vessels, A and B, contain water up to the same level as shown in the Figure.
P_A and P_B are the pressures at the bottom of the vessels.
F_A and F_B are the forces exerted by the water at the bottom of the vessels A and B.

(1) $P_A=P_B,F_A=F_B$

(2) $P_A=P_B,F_A<F_B$

(3) $P_A<P_B,F_A=F_B$

(4) $P_A>P_B,F_A>F_B$

Answer
(b) $P_A=P_B,F_A<F_B$

• In the figure, both vessels A and B contain water up to the same level. Therefore, the pressure at the bottom of the two vessels must be equal: P_A=P_B
• The formula for force is: F = P × A
Where A is the area of the bottom surface. Since, P_A=P_B, the force ratio depends on the areas AA and AB.

By observing the figure, the bottom area of vessel A (AA) is smaller than the bottom area of vessel B (AB).

Since,(F _{ A }= P _{ A } \times A _{ A } and (F _{ B }= P _{ B } \times A _{ B }, and A _A< A _B, it follows that: $F_A<F_B$

Combining the results, P_A=P_B and F_A<F_B.

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) The weather is stormy at the eye of a cyclone.
(iv) During a thunderstorm, it is safer to be in a car.

Answer
(i) True
(Air flows from a region of higher pressure to a region of lower pressure.)

(ii) False
(liquids exert pressure in all directions, including on the walls of the container.)

(iii) False
(it is calm at the eye of a cyclone.)

(iv) True
(Yes, it will be safer to be in a car during a thunderstorm)

3. Figure (a) shows a boy lying horizontally, and Figure (b) shows the boy standing vertically on a loose sand bed. In which figure does the boy sink more into the sand? Give reasons.

Answer - The boy in Figure (b) will sink more. The weight of the boy is the same, but in Fig. (a), the force (of the weight) is acting on a large area. The pressure in this case is less. In Fig. (b), the same force (of the weight) is acting on a small area. The pressure, therefore, is more. The boy will sink more into the sand in this case.

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.

Answer - Force (the weight) of the elephant acting on the ground = 20000 N

Area on the ground covered by the four feet of the elephant
= 4 × 0.25 m² = 1 m²

Pressure exerted by the elephant on the ground
= Force / Area
= 20000 N / 1 m²
= 20000 Pa

5. There are two boats, A and B. Boat A has a base area of 7 m², and 5 persons are seated in it. Boat B has a base area of 3.5 m², and 3 persons are seating in it. If each person weighs 700 N, find out which boat will experience more pressure on its base and by how much?

Answer
Force of the weight of 5 persons acting on the base of boat A
= 5 × 700 N = 3500 N

Base area of boat A = 7 m²

Pressure exerted on the base of boat A
= Force / Area
= 3500 N / 7 m²
= 500 Pa

Force of the weight of 3 persons acting on the base of boat B
= 3 × 700 N = 2100 N

Base area of boat B = 3.5 m²

Pressure exerted on the base of boat B
= Force / Area
= 2100 N / 3.5 m²
= 600 Pa

Therefore, boat B will experience more pressure on its base by 100 Pa.

6. Would lightning occur if air and clouds were good conductors of electricity? Give reasons for your answer.

Answer
In case the air and the clouds were good conductors of electricity, the charges could not accumulate in the clouds (because they would flow into the air), there would be no charge buildup, which is necessary for lightning to occur. Therefore, if air and clouds were good conductors of electricity, lightning would not occur.

7. What will happen to the two identical balloons A and B as shown in Figure when water is filled into the bottle up to a certain height? Will both the balloons bulge? If yes, will they bulge equally? Explain your answer.

Answer - When water is filled into the bottle up to a certain height (sufficiently above the level of the entry points of water from the bottle) both the balloons will bulge. The entry points of water from the bottle to the balloons are at the same height. The balloons, being elastic, exert some force on the water. Assuming that the balloons are equally elastic, both balloons will bulge equally.

8. Explain how a storm becomes a cyclone.

Answer - Cyclones are large storms that form over warm ocean waters.

• As the ocean water gets heated, the air above it becomes moist and warm and rises to a height where water vapor condenses to form raindrops.
• Condensing water vapor releases heat back into the atmosphere.
• This further warms the ascending air, leading to its further rise, creating an even lower pressure.
• Air from the surrounding regions rushes in, and it also starts rising.
• The moving air starts to spin under the influence of the Earth’s rotation.
• This cycle is repeated, resulting in the creation of a very low-pressure area with high-speed winds revolving around it.
• This spinning system of clouds, winds, and rain is called a Cyclone.

9. The figure shows trees along the sea coast on a summer afternoon. Identify which side is land – A or B. Explain your answer.

Answer - During the daytime on a summer afternoon, there is a sea breeze that blows from sea to land. This happens because the land gets heated faster and the air above land rises resulting in low-pressure region over land. Cooler air over sea moves from high-pressure region towards the land. The bending of trees due to wind, as shown in the figure, suggests that wind is blowing in the direction from B to A. This suggests ‘A’ side is land.

10. Describe an activity to show that air flows from a region of high pressure to a region of low pressure.

Answer - Activity to show that air flows from a region of high pressure to a region of low pressure.

Materials required: Two similar balloons made of thin rubber, a drinking straw, and some thread.

Procedure:
• Insert one end of the straw into one balloon and secure it with the thread.
• Inflate the second balloon and insert the free end of the straw into the neck of the inflated balloon, and secure it with the thread. (Ensure that the air from the inflated balloon does not leak.)

Observations: Some air moves from the inflated balloon to the uninflated balloon, and the sizes of both balloons change. After some time, both the balloons attain almost the same size, and the flow of air stops.

Conclusion: The inflated balloon has higher pressure inside it, and the uninflated balloon has low pressure inside. When the two balloons are connected through a straw, air moves from the high-pressure area (inside the inflated balloon) to the low-pressure area (inside the uninflated balloon).

11. What is a thunderstorm? Explain the process of its formation.

Answer
(i) During the rainy season, when land gets heated in hot, humid, and tropical regions of India, the warm and moist air being lighter rises, thus creating a low-pressure area. Cooler air from surrounding high-pressure areas flows to take its place. This air again gets heated and rises, thereby resulting in a continuous process of wind circulation. As the rising air expands, it cools and moisture in it condenses to form water droplets forming clouds. The water droplets merge to form heavier drops, which come down as rain, hail, or snow. The strong winds accompanied by rain are called a storm.

(ii) During a storm formation, under certain conditions, warm air rises to great heights, and the low temperature there changes water droplets into ice particles. Strong winds blowing upwards and downwards result in rubbing between water droplets and ice particles. This generates electric charges within clouds. Ice particles are positively charged, and they move upwards in the upper part of the clouds. Water droplets are negatively charged and occupy the lower part of the clouds.

When negatively charged water droplets in the lower part of the cloud move closer to the ground, trees, buildings, and the ground become positively charged. Normally, air acts as an electrical insulator and does not let opposite charges meet. This insulating property of the air breaks down when the build-up charges becomes very large. A sudden flow of charges takes place, resulting in a bright flash of light called lightning. Lightning can occur as opposite charges collide within a cloud, between clouds, or between clouds and the ground. Lightning rapidly heats the air around it. This results in expansion of air to produce a loud sound called thunder. A storm accompanied by lightning and thunder is called a thunderstorm.

12. Explain the process that causes lightning.

Answer
During a storm formation, under certain conditions, warm air rises to great heights, and the low temperature there changes water droplets into ice particles. Strong winds blowing upwards and downwards result in rubbing between water droplets and ice particles. This generates electric charges within clouds. Ice particles are positively charged, and they move upwards in the upper part of the clouds. Water droplets are negatively charged and occupy the lower part of the clouds. When negatively charged water droplets in the lower part of the cloud move closer to the ground, the trees, buildings, and the ground become positively charged. Normally, air acts as an electrical insulator and does not let opposite charges meet. This insulating property of the air breaks down when the build-up charges becomes very large. A sudden flow of charges takes place, resulting in a bright flash of light called lightning. Lightning can occur as opposite charges collide within a cloud, between clouds, or between clouds and the ground. Lightning rapidly heats the air around it. This results in expansion of air to produce a loud sound called thunder.

13. Explain why holes are made in banners and hoardings.

Answer - Holes made in banners and hoardings save these from blowing off with high-speed winds. High-speed winds are accompanied by a reduced pressure. If there are no holes in the banners or hoardings, they block the wind, but the wind blows on the sides of these banners and hoardings. This forms low-pressure area on sides and opposite side of the banners/hoardings. There remains a high-pressure area on the side of the banner or hoarding that faces the direction from which wind is blowing. When the pressure difference is large the banners or the hoardings are blown away. With the holes in the banners or hoardings, the wind blows through these holes, and the pressure difference is minimised, keeping them intact.

3.0Key Topics Covered in Class 8 Science Chapter 6 – Pressure, Winds, Storms, and Cyclones

1. The Nature of Air Pressure: Understanding that air exerts pressure in all directions and flows from high-pressure regions to low-pressure regions.
2. Liquid Pressure: Learning that pressure in liquids increases with depth and height, acting on both the bottom and the walls of a container.
3. Atmospheric Phenomena:

• Wind Generation: How uneven heating of the Earth creates pressure differences that lead to air movement.
• Thunderstorms: The formation of storms through rising warm air, moisture condensation, and the generation of lightning and thunder.
• Cyclones: The development of massive spinning systems over warm ocean waters driven by low-pressure centres.

4. Practical Physics: The science behind everyday objects like rubber suckers and the structural necessity of holes in outdoor banners.

4.0Benefits of Studying Class 8 Science Chapter 6 – Pressure, Winds, Storms, and Cyclones

• Safety Awareness: Students will learn the most important safety guidelines, such as: during a thunderstorm, it is safer to stay inside the vehicle.
• Predictive Skills: Students will learn how to interpret the weather by recognising wind patterns and how to interpret changes in wind direction as well as what to look for in the environment.
• Engineering Basics: Understand pressure changes; understand how pressure differences help to determine types of structural design; understand the reason for holes in hoardings so that high winds do not blow them away.
• Scientific Calculator: Students learn the mathematical formula that calculates physical impact based on the amount of force applied to the surface area of a given object, ranging from weighing an elephant to how much pressure a boat experiences on its hull.