CBSE Important Questions Class 8 Science Chapter 6 – Pressure, Winds, Storms and Cyclones

Class 8 Science Chapter 6 Pressure, Winds, Storms and Cyclones is part of the new NCERT Curiosity textbook. It explains what pressure is, how air exerts pressure on everything around us, and how differences in air pressure make the wind blow. Students learn why warm air rises, how land and sea breezes form, how thunderstorms and cyclones develop, and what safety steps should be taken during a storm.

These CBSE important questions for Class 8 Science Chapter 6 cover air circulation in a room with a heater, assertion-reason questions on thunderclouds and the rotation of the Earth, why storms bring strong winds, the paper-strip experiment showing that fast-moving air has low pressure, how a sea breeze forms, how a cyclone develops and the safety measures to follow. Every question has a clear step-by-step answer in simple English, so students can practise on their own, parents can check the answers, and teachers can use them for class tests.

Q1. In a room with a heater on one side and an open window on the other, how will air circulate?
(a) Air will flow from heater to window at all levels
(b) No circulation will occur
(c) Warm air will rise near the heater; cool air will enter from the window at a lower level
(d) Air will move randomly

Answer: (c) Warm air will rise near the heater; cool air will enter from the window at a lower level
Air near the heater becomes hot, expands and becomes lighter, so it rises. This leaves a region of low pressure near the floor. Cooler, denser air from the window moves in at the lower level to take its place. This sets up a continuous current of air called a convection current.

Q2. Read the Assertion (A) and Reason (R) and choose the correct option.
Assertion (A): Thunderclouds grow vertically rather than spreading sideways.
Reason (R): Warm moist air rises rapidly during thunderstorm formation.
(a) Both A and R are true, and R is the correct explanation of A
(b) Both A and R are true, but R is not the correct explanation of A
(c) A is true but R is false
(d) A is false but R is true

Answer: (a) Both A and R are true, and R is the correct explanation of A
In a thunderstorm the warm moist air near the ground shoots upwards very fast. As this rising air carries the water vapour higher and higher, the cloud builds upwards instead of spreading out flat. So the rapid upward movement is exactly the reason for the tall, towering shape of thunderclouds.

Q3. Read the Assertion (A) and Reason (R) and choose the correct option.
Assertion (A): Winds do not always blow in straight lines.
Reason (R): The rotation of the Earth affects the movement of air.
(a) Both A and R are true, and R is the correct explanation of A
(b) Both A and R are true, but R is not the correct explanation of A
(c) A is true but R is false
(d) A is false but R is true

Answer: (a) Both A and R are true, and R is the correct explanation of A
Winds curve rather than travelling straight. This happens because the Earth keeps rotating while the air is moving, which bends the path of the wind. So the rotation of the Earth is the correct explanation for the curved paths of winds.

Q4. Dark clouds gathered suddenly, followed by strong winds and heavy rain. Apply your understanding to explain why storms cause strong winds.

Answer: A storm is caused by a very large difference in air pressure between two regions.
Air always moves from an area of high pressure towards an area of low pressure. The bigger this difference, the faster the air rushes in. In a storm the pressure at the centre falls very low, so air from the surrounding high-pressure region rushes in at great speed, and we feel this as strong wind.

Q5. Two paper strips were hung close to each other. When students blew air between them, the strips moved closer instead of moving apart. Apply pressure concepts to explain why.

Answer: When air is blown between the strips, it moves very fast through that narrow gap.
Fast-moving air exerts lower pressure than still air. So the pressure between the strips becomes less than the pressure of the still air on their outer sides.
The higher pressure outside pushes the strips inward, and that is why they come closer instead of moving apart.

Q6. On a hot summer afternoon, strong winds blew from the sea towards the land. Apply the concept of air pressure to explain how a sea breeze forms.

Answer: During the day the land heats up much faster than the sea, because water takes longer to warm up.
The air above the hot land becomes warm, expands and rises, creating a low-pressure area over the land.
The air over the sea stays cooler and denser, so it is at higher pressure.
Air then moves from the sea towards the land to fill the gap. This cool wind blowing from the sea to the land during the day is called the sea breeze.

Q7. What is a land breeze? How is it different from a sea breeze?

Answer: At night the land cools down faster than the sea. So the air over the sea is now warmer, rises and creates a low-pressure area there, while the air over the cooler land is at higher pressure. Air therefore moves from the land towards the sea. This is called the land breeze.
Difference: a sea breeze blows from the sea to the land during the day, while a land breeze blows from the land to the sea at night. Both are caused by the land and the sea heating and cooling at different rates.

Q8. Define pressure. Write its formula and SI unit. Why is the base of a dam made thicker than its top?

Answer: Pressure is the force acting on a unit area of a surface.
Pressure = Force ÷ Area
Its SI unit is the pascal (Pa), where 1 Pa = 1 N/m².
The base of a dam is made thicker because the pressure of a liquid increases with depth. The water at the bottom of the reservoir presses on the wall with far greater pressure than the water near the top, so the lower part of the dam must be much stronger and thicker to withstand it.

Q9. How is a cyclone formed? Name any two safety measures that should be taken during a cyclone.

Answer: Formation: Over a warm sea, water evaporates quickly and the warm moist air rises. As this air goes up, it leaves a region of very low pressure below. Air from around rushes in, and it too becomes warm and rises. The water vapour condenses higher up and releases heat, which makes the air rise even faster. The whole system starts to spin because of the rotation of the Earth, and a cyclone is formed with a calm centre called the eye.
Safety measures:
1. Listen to the warnings given on radio, television and by the weather department, and move to a safe shelter if told to do so.
2. Do not go out during the storm, keep away from loose electric wires and damaged buildings, and store drinking water and dry food in advance.

Q10. Why does a cyclist feel more tired while cycling against the wind?

Answer: When a cyclist rides against the wind, the moving air pushes against the cyclist and the cycle in the direction opposite to their motion. This push is the force of air resistance, which is a kind of friction.
To keep moving forward, the cyclist has to work harder to overcome this extra opposing force, so more energy is used and the cyclist gets tired quickly. While cycling with the wind, the air pushes from behind and helps, so it feels much easier.

Q11. Why do we feel that air has no weight, even though it exerts pressure on us?

Answer: Air does have weight, and the column of air above us presses on our body with a pressure of about 100,000 Pa, which is a very large force.
We do not feel it crushing us because the pressure inside our body is equal to the air pressure outside. The air pushes on us from every side, and the inside pressure balances it. Since the forces cancel one another, we feel nothing at all, and this makes us think air has no weight.

Q12. Why does a tin can get crushed when the air inside it is removed?

Answer: Normally the air inside the can pushes outwards with the same pressure as the air outside pushes inwards, so the two balance and the can keeps its shape.
When the air inside is removed, there is nothing left to push outwards. The air outside keeps pressing on the can from all sides with full atmospheric pressure. With no balancing force from inside, this outside pressure is enough to crush the can. This experiment shows that air really does exert a strong pressure.

Related Study Material on Extramarks

Q.1 There are four situations in which a block is experiencing a set of forces as shown below. The net force is known for each situation. However, the magnitudes of a few of the individual forces are not known.

Analyze each situation individually and determine the magnitude of the unknown forces.

Marks:5
Ans

A = 50 N, so that the horizontal forces must be balanced.
B = 200 N, so that the vertical forces must be balanced.
C = 1100 N, in order to have a net force of 900 N in the upward direction.
D = 20 N, in order to have a net force of 60 N to the left.
E = 3000 N, so that the vertical forces must be balanced.
F = H = it can take any number but the value of both of them should be equal, in order to balance the vertical forces.
G = 50 N, in order to have a net force of 30 N to the right.

Q.2 Mention three types of forces that can act from a distance.

Marks:3
Ans

Three types of forces which can act from a distance are :
1. Magnetic force.
2. Electrostatic force.
3. Gravitational force.

Q.3 Define atmospheric pressure.

Marks:1
Ans

The atmospheric air is present up to many kilometers above the surface of the earth. The pressure exerted by this air is known as atmospheric pressure.

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