Go through BSE Odisha Class 8 Science Solutions Chapter 6 Pressure, Winds, Storms, and Cyclones Question Answer to understand textbook questions more clearly.
Class 8 Science Curiosity Chapter 6 Question Answer
Class 8 Science Ch 6 Pressure, Winds, Storms, and Cyclones Question Answer
Class 8 Science Chapter 6 Pressure, Winds, Storms, and Cyclones Question Answer
Probe and Ponder Questions
Question 1.
Why are winds stronger on some days than on others?
Answer:
Winds are stronger on some days due to greater differences in air pressure (pressure gradients) between different locations. When a weather system, such as storm or a cyclone, creates steep pressure differences, air moves rapidly from high-pressure areas to low-pressure areas, resulting in strong winds. Temperature contrasts (such as between land and sea, or during weather fronts), and local topography can intensify these differences and wind speeds.
Question 2.
Why are water tanks usually placed at a height?
Answer:
Water tanks are placed at a height so that water can flow down easily with pressure due to gravity, ensuring a steady supply to all parts of a building or area without needing extra pumping.
Question 3.
Can air pressure really crush us?
Answer:
No, air pressure cannot crush us because the pressure inside our bodies is equal to the air pressure outside. The atmosphere presses on us with great force, but our body fluids and gases push outward with the same amount of pressure, keeping everything balanced. That’s why we don’t feel the weight of the air or get crushed by it under normal conditions on Earth.
Question 4.
What causes storms and cyclones? If the Earth stopped rotating, would cyclones still form?
Answer:
Storms and cylones are formed when warm, moist air from the sea rises and cools, causing strong winds and heavy rain. The spinning of the Earth makes these winds rotate, forming a cyclone. If the Earth stopped rotating, there would be no spinning effect, so cyclones would not form, though normal storms could still happen.
Question 5.
Share your questions ………………
Answer:
Possible questions you might ask after exploring these ideas:
- Why don’t we feel atmospheric pressure even though it is so high?
- How do buildings and bridges withstand strong winds during storms?
- Do animals sense changes in air pressure before storms?
- What scientific instruments are used to measure wind speed and pressure?
- How do disaster warning systems work for cyclones?
InText Questions
Question 1.
Why do fall leaves rise in the air or trees bend when a strong wind blows? (Page 81)
Answer:
The force exerted by the wind creates wind pressure, which causes fallen leaves to rise in the air and the bending or swinging of trees when a strong wind blows.
Question 2.
Can the shape or size of the straps make a difference, provided both bags are equally heavy? (Page 81)
Answer:
When we carry a bag, we feel its weight because of the force of gravity acting on our shoulders. The weight of the bag with narrow straps acts on a smaller area of our shoulders, whereas the weight of the bag with broad straps is spread over a larger area of our shoulders. Although both bags have equal weight, we feel more comfortable carrying a bag with broad straps. Broad straps reduce the pressure exerted by the bag on the shoulders.
Question 3.
Do liquids also exert pressure? (Page 83)
Answer:
Yes, liquids also exert pressure. The pressure from a liquid acts in all directions and increases with depth – the deeper you go, the greater the pressure.
Question 4.
What will happen to the bulge of the balloon if we increase the height of the water column? (Page 84)
Answer:
If we increase the height of the water column, the bulge of the balloon will become bigger because the pressure of the water increases with height, pushing more strongly on the balloon.
Question 5.
(a) Why are overhead tanks kept at a height?
(b) Suppose you are living on the second floor of a three-story building and an overhead tank is placed on the top floor. Will you or your friend on the first floor receive a more powerful stream of tap water? Give reasons. (Page 84)
Answer:
(a) Overhead tanks are placed at a height so that the pressure in the taps is increased, resulting in a good stream of water from the taps.
(b) Pressure exerted by water increases with the increase of height of the liquid column. Suppose I live on the second floor of the building that has three floors, and the overhead tank is installed on the top floor. The pressure of water and hence the power of water stream from the taps will depend on the height of the overhead tank above the taps of the second floor. My friend living on the first floor will have a longer distance from the taps to the overhead tank, which means the height of the water column above his taps will be more compared to my water taps on the second floor. Therefore, my friend will receive more powerful stream of tap water.
Question 6.
Why does water spurt out like a fountain from leaking joints or holes in water pipes? (Page 85)
Answer:
Water in water pipes has long water columns, as the water tanks to which the water pipes are connected are placed at heights. The pressure inside the pipes is high. The water exerts pressure in all sides of the container including the bottom and walls of the pipe. When this water exerting pressure on all sides, finds a narrow opening like a hole or a leaking joint, it spurts like a fountain.
Question 7.
What happens when an inflated balloon is kept without closing its mouth? (Page 86)
Answer:
The inflated balloon has air inside, which exerts pressure on the walls of the balloon, resulting in expansion of the balloon on all sides. The elastic walls of the balloon exert equal but opposite pressure on the air. When we keep the inflated balloon without closing its mouth, the air from within the balloon escapes through its mouth from high pressure inside the balloon to low pressure outside the balloon.
Question 8.
Does the difference in air pressure have anything to do with the formation of winds? (Page 88)
Answer:
Air moves from a high-pressure region to a low-pressure region. Moving air is called wind. Thus, it is the difference in air pressure that results in the formation of wind.
Pressure, Winds, Storms, and Cyclones Class 8 Questions and Answers
Keep the Curiosity Alive (Pages 94-96)
Question 1.
Choose the correct statement.
(i) Look at 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
Reason: The level of water in connected vessels (communicating vessels) will be the same regardless of shape, as liquid pressure depends on the height of the column, not the vessel’s shape or width.
(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.
Answer:
(c) M will stick but N will not stick.
Reason: The rubber sucker sticks due to atmospheric pressure creating a vacuum on a smooth surface. On a rough surface, air leaks in, preventing the vacuum and thus the sticking.
(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.
Reason: Liquid pressure increases with the height of the water column. Raising the tank increases the pressure, resulting in a stronger stream of water.
(iv) Two vessels, A and B contain water up to the same level as shown in figure. 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
Answer:
(b) PA=PB, FA<FB
Reason: Pressure at the bottom depends on the height of the water, which is the same in both vessels, so PA=PB. Force equals pressure times area; since vessel A is narrower (smaller area), FA<FB.
Question 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.
Answer:
True.
(ii) Liquids exert pressure only at the bottom of a container.
Answer:
False (liquids exert pressure in all directions, including on the walls of the container.)
(iii) Weather is stormy at the eye of a cyclone.
Answer:
False (it is calm at the eye of a cyclone)
(iv) During a thunderstorm, it is safer to be in a car.
Answer:
True.
Question 3.
Figure (a) shows a boy lying horizontally, and Figure (b) shows the boy standing vertically on a loose sand bed. In which case does the boy sink more in 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.
Question 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
= \(\frac{\text { Force }}{\text { Area }}=\frac{200000 \mathrm{~N}}{1 \mathrm{~m}^2}\)=20000 Pa
Question 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 has a weight of 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
\(= \frac{\text { Force }}{\text { Area }}=\frac{3500 \mathrm{~N}}{7 \mathrm{~m}^2}\) = 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 = 3.0 m2
Pressure exerted on the base of boat B
= \(\frac{\text { Force }}{\text { Area }}=\frac{2100 \mathrm{~N}}{3.5 \mathrm{~m}^2}\) =600Pa
Therefore, boat B will experience more pressure on its base by 100 Pa.
Question 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.
Question 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.
Question 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.
Question 9.
The figure shows trees along the sea coast in 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 a low-pressure region over land. Cooler air over sea moves from the 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.
Question 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).
Question 11.
What is a thunderstorm? Explain the process of its formation.
Answer:
(a) A Thunderstorm is a storm that produces thunder, lightning, heavy rain, and strong winds. It usually occurs during hot weather when the atmosphere becomes unstable.
(b) During a thunderstorm 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.
Question 12.
Explain the process that causes lightning.
Answer:
During a thunderstorm 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.
Question 13.
Explain why holes are made in banners and hoardings.
Answer:
Holes are made in banners and hoardings to save them 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.
Class 8 Science Chapter 6 Question Answer
Activity 1.
Aim: To show that the pressure exerted by water at the bottom of the container depends on the height of its column.
Materials Required: Two rubber balloons, glass or plastic pipes of different diameters.
Procedure:
Case I: When two pipes are of different diameters.
- First of all we will take two transparent glass or plastic pipes of the same length (about 25 cm), these pipes must be of different diameters, as shown in fig.
- Now, we will take two good-quality rubber balloons and attach them to one end of each pipe.
- Clamp the pipes on a stand as shown in fig. (1)
- Now, fill both the pipes with water up to the same level about halfway.
Case II: When two pipes are of same diameters.
- Take two pipes of same length and same diameter.
- Now, pour water in both the pipes.
- Water should be at different leves in the pipes. See fig. (2) Note down your observations.
Observations:
- When the water levels in both pipes are same. Two balloons bulge to the same extent.
- Higher heights of water column produce bigger bulge of the balloon.
Inferences:
- More height of water column produce bigger buldge (i.e., bulge of balloon increases as the height of water column increases).
- Bulging of balloons do not depends on the diameters of the pipes. It depends on height of water column.
- Hence, the pressure due to liquid increases with height of water column.
Activity 2.
Let us find out
Aim: To show that a liquid exert pressure on the walls of the container and also equal pressure at the same depth.
Materials Required: An empty plastic bottle, water, a needle or a nail.
Procedure:
- Take an empty plastic bottle.
- Drill four holes near the bottom of the bottle using a needle or a nail.
- Now, seal the holes with a tape and fill the bottle with water.
- Make sure that the holes are at the same height from the bottom.
- Â Remove the tape from all holes at the same time.
Observations:
- Water flowing out from the holes on the side of the bottle.
- Different streams of water coming out of the holes falls at the same distance from the bottle.
Inference:
- Therefore, we can conclude that liquids exert pressure not only at the bottom of the container, but also on its sides. In fact liquids exert pressure in all directions.
- Liquid exert equal pressure at same depth.
Activity 3.
Let us explore
Aim: To show that air exert pressure.
Materials Required: A paper plate, two identical chart paper of size about 70 cm × 56 cm
Procedure:
- First of all we will take a paper plate and invert it and attach a stick to it see fig. (a).
- Now place it on a plain wooden surface.
- Then, take two sheets of chart paper of same size 70cm × 56cm each. Fold one sheet twice and make a hole in the centre of the folded chart paper sheet – big enough for the stick to come out. Place the folded sheet on top of the inverted paper plate as see fig. (b).
- Now, try to lift the paper plate covered with a folded sheet using the stick.
- What did you observed ? How much effort is needed to lift it.
- Now, put the second unfolded chart paper sheet in place of the folded sheet. Make a hole at the centre of this chart paper for the stick to pass through. Cover the paper plate with the unfolded chart paper as shown in fig. (c).
- Try to lift the paper plate once again and feel the effort needed to do so.
- Which of the above case, with the folded or the unfolded is easy to lift, either chart paper covering the paper plate.
Observations:
- We feel more effort to lift the paper plate when it is covered with the unfolded chart paper, than with the folded chart paper.
- The larger the surface area covered, the greater the force needed to life the plate.
Inference:
- Air exert force on the covering sheet.
- Force increases with increase in the area of covering sheets.
- It is clear that air is exerting a force on the paper plate, which increases as the area of the sheet covering it increases.
Activity 4.
Let us perform
Aim: To show the effect of pressure due to air.
Materials Required: A good quality rubber sucker.
Procedure:
- Take a good quality rubber sucker. It looks like a small rubber cup.
- Press it hard on a smooth, plane surface.
- Does it stick to the surface ? Yes, it sticks to the surface very hard.
- Now, try to pull it off the surface. Do you find it difficult to pull it off ?
Observations: It is very difficult to pull off a rubber sucker.
Inference:
- All gases exert pressure.
- The sucker sticks to the surface because the pressure of air surrounding the sucker is higher than the pressure exerted by the air inside the sucker.
Activity 5.
Let us observe
Aim: To show that air (winds) blows untill there is a pressure difference. (i.e., from a high pressure region to low pressure region)
Materials Required: Two balloons of same size, a drinking straw, thread.
Procedure:
- First of all we will take two balloons made of thin rubber of same size and a drinking straw.
- Now, we will insert one end of the straw into one balloon and tie its mouth properly with a rubber band or thread.
- Now, we will inflate the second balloon and hold its mouth with our fingers, in such away that air does not escape.
- Now, insert the free end of the straw into the neck of the inflated balloon and tie it with a rubber band or thread.
- We should take precaution at the time of insertion of straw that there is no leakage of air from the balloons.
- Now, we can see in fig. that one end of the straw is inside the inflated balloon and the other end inside the uninflated balloon.
Observations:
- Size of uninflated balloon increases and that of inflated balloon decreases.
- After sometime both the balloons attain almost the same size and flow of air stops.
Inference:
- We can conclude that the air pressure in the inflated balloon is higher than that in the uninflated balloon. So, air moves from the inflated balloon to the uninflated balloon, resulting in changes in the size of these two balloons.
- The air flow stops when the pressure in both balloons becomes equal.
- Hence, it shows that air moves or blows untill there is a pressure difference.
Activity 6.
Let us observe
Aim: To show that high speed winds are due to a reduced air pressure.
Materials Required: Two balloons of same size, string or thread, a stick.
Procedure:
- Take two balloons of the same size.
- Now, inflate both balloons and tie strings to them.
- Take a stick and hang the two balloons from it.
- We must leave a gap of 6-10 cm (See fig.).
- Now, blow air with your mouth into the narrow space between the balloons.
- What happens to the balloons? Note down your observations.
- Now blow harder and observe.
Observations:
- Both balloons move towards each other.
- When we blow harder the balloons approaches towards each other with more speed.
Inference:
- When you blow air between the balloons, a low pressure area is created between them.
- We conclude that high speed winds are accompanied by a reduced air pressure.
Pressure, Winds, Storms, and Cyclones Class 8 Extra Questions and Answers
Short Answer Type Questions
Question 1.
Why school bags have wide straps ?
Answer:
A school bag has wide strap so that the weight of a bag may fall over a large area of the shoulder of the child producing less force on the shoulder. Due to less pressure, it is more comfortable to carry the heavy school bag.
Question 2.
Why is the bottom part of the foundation of a building made wider ?
Answer:
Foundation of a building is made wider so that it may not sink under the extremely high pressure of building. The wider foundation distributes the weight of the building over a large area on the ground.
Question 3.
Why cutting instruments are sharpened?
Answer:
All cutting instruments such as blades, axes etc., are sharpened so that the area of cross-section decreases and hence pressure exerted by them increases. Thus they can easily cut and penetrate a given surface.
Question 4.
Calculate the pressure if a force of 8 N is applied on an area of 2 cm2
Answer:
Force =8 N
Area =2cm2
[ ∵ 1cm2= \(\frac{1}{10,000}\)=\(\frac{2 \mathrm{~m}^2}{10,000}\)
Pressure = \(\frac{8}{2 / 10,000}=40,000 \mathrm{~N} / \mathrm{m}^2 \)
Question 5.
Why a sharp knife cuts better than a blunt knife?
Answer:
A sharp knife cuts objects (like vegetables) better because due to its very thin edge, the force of our hand falls over a very small area of the object producing a large pressure. This large pressure cuts the object easily. On the other hand, a blunt knife has a thicker edge. A blunt knife does not cut an object easily because due to its thicker edge, the force of our hand falls over a larger area of the object and produces lesser pressure. This lesser pressure cuts the object with difficulty.
Question 6.
Why does water spurt out like a fountain from leaking joints or holes in water pipes?
Answer:
Water spurting out like a fountain from holes because:
- Water pipes are connected to tank at certain height by a long pipes and create a long water column and the pressure inside the pipes is high.
- Liquid exert pressure not only at the bottom of the container, but also on its side, i.e., liquid exert pressure in all directions. Due to the pressure exerted by water on the walls of the pipes we have seen water spurting out like a fountain from leaking joints or holes in water pipes.
Question 7.
How does rubber sucker stick to the surface like wall ?
Answer:
The sucker sticks to the surface because the pressure of air surrounding the sucker is higher than the pressure exerted by the air inside the sucker. To pull the sucker off the surface, the applied force should be strong enough to overcome the pressure difference between outside the sucker and inside the sucker.
Question 8.
Why do mountainers suffer from nose-bleeding at higher altitudes?
Answer:
This is because, at higher altitude, the atmospheric pressure suddenly drops. This leads to the rapture of blood vessels in the body causing bleeding from the nose.
Question 9.
How do thunderstorms produce lightning through charge separation?
Answer:
Strong updrafts and downdrafts make water droplets and ice rub and become charged, with opposite charges separating within the cloud. When the charge difference becomes very large, a sudden discharge occurs as lightning.
Long Answer Type Questions
Question 1.
Why it is easier to walk on soft sand if we have flat shoes rather than shoes with sharp heels (or pencil heels) ?
Answer:
This is because a flat shoe has a greater area in contact with the soft sand due to which there is less pressure on the soft ground. Due to this the ‘flat’ shoes do not sink much in soft sand and it is easy to walk on it.
On the other hand, a sharp heel has a small area in contact with the soft sand and so exerts a greater pressure on the soft sand. Due to this greater pressure, the sharp heels tend to sink deep into soft sand making it difficult for the wearer to walk on soft sand.
Question 2.
It is difficult to cut cloth using a pair of scissors with blunt blades. Explain.
Answer:
We know that more area of contact will produce less pressure and vice-versa. Blunt blades have larger area as compared to the sharp-edged blades. Thus, the applied force produces a lower pressure in case of blunt blades, which makes it difficult to cut the cloth.
Question 3.
Two rods of the same weight and equal length have different thickness. They are held vertically on the surface of sand as shown in figure. Which one of them will sink more? Why?
Answer:
Since rod B is thinner than ‘A’. Therefore, rod B will go more deeper as it has a smaller area of contact, therefore the same force (weight of the rod) will produce more pressure. But in case of rod A the same force produces less pressure.
Question 4.
Two women are of the same weight. One wears sandals with pointed heels while the other wears sandals with flat soles. Which one would feel more comfortable while walking on a sandy beach? Give reasons for your answer.
Answer:
Two women are of the same weight but the woman wearing sandals with flat soles will feel more comfortable while walking on the sandy beach. Because, the flat soles have larger area as compared to the sandals with pointed heels. Here, the two women are of the same weight, they will apply same force on the ground.
Hence, the pressure exerted by the pointed heels will be more compared to that with sandals having flat soles. So, the pointed heel sandals will sink more in the sand than the flat sole sandals. Hence, walking with flat sole sandals will be more comfortable.
Question 5.
It is much easier to burst an inflated balloon with a needle than by a finger. Explain.
Answer:
Smaller area produces large pressure. When we prick the surface of an inflated balloon with a needle it exerts a large pressure because it has a smaller area of contact compared to the finger. So, the large pressure pierces the surface of the balloon easily.
Case-Study Based Questions
1. Read the following passage carefully and answer the questions that follow:
Our earth is surrounded by a large amount of air consisting of Nitrogen, Oxygen, Argon, Carbon dioxide and traces of other gases. Layers of air surrounding the earth are called the atomsphere.
(a) What is atmosphere?
Answer:
The layers of air surrounding the earth are called the atmosphere.
(b) What is atmospheric pressure?
Answer:
The pressure exerted by air on the surface of the earth is known as the atmospheric pressure.
(c) Is the pressure inside our bodies equal to the atmospheric pressure? Why are we not crushed?
Answer:
Yes, the pressure inside our bodies balances the outside pressure of the atmosphere. That is why we are not crushed under the atmospheric pressure.
Picture Based Questions
I. Observe the picture and answer the questions.
(i) Do the different streams of water coming out of the holes fall over it the same distance from the bottle?
(a) Different distance
(b) Same distance
(c) Two holes same distance
(d) None of these
Answer:
(b) Same distance
(ii) Does liquid exert equal pressure on the same depth?
(a) No
(b) Some times
(c) Yes
(d) 50-50
Answer:
(c) Yes
(iii) What does this indicate?
Answer:
This indicates that liquids exert equal pressure at the same depth.
Pressure, Winds, Storms, and Cyclones Class 8 MCQ
Multiple Choice Questions (Mcqs)
Question 1.
What is the SI unit of pressure ?
(a) N/m2
(b) Newton (N)
(c) N/m
(d) m2
Answer:
(a) N/m2
Question 2.
Bulging of balloons depends on :
(a) height of water or liquid column
(b) diameter of pipes
(c) weight of liquid or water
(d) none of these
Answer:
(a) height of water or liquid column
Question 3.
The sucker sticks to the surface because :
(a) the pressure of air surrounding the sucker is lower than the pressure exerted by air inside the sucker.
(b) the pressure of air is equal to the pressure inside the sucker.
(c) the pressure of air outside is higher than the air pressure inside the sucker
(d) none of these
Answer:
(c) the pressure of air outside is higher than the air pressure inside the sucker
Question 4.
1 hectopascal (hpa) is equal to :
(a) 10 Pa
(b) 50 Pa
(c) 100 Pa
(d) 1000 Pa
Answer:
(c) 100 Pa
Question 5.
Figure shows a container filled with water. Which of the following statements is correct about pressure of water?
(a) Pressure at A> Pressure at B> Pressure at C
(b) Pressure at A= Pressure at B= Pressure at C
(c) Pressure at A<Pressure at B>Pressure at C
(d) Pressure at A<Pressure at B<Pressure at C
Answer:
(d) Pressure at A<Pressure at B<Pressure at C
Assertion and Reasoning
These questions consist of two statements, each printed as Assertion (A) and Reason (R). While answering these questions, you are required to choose any one of the following four responses.
(a) Assertion (A) and Reason (R) both are correct and reason is correct explanation for assertion.
(b) Assertion (A) and Reason (R) both are correct and reason is not correct explanation for assertion.
(c) Assertion (A) is correct but the Reason (R) is wrong.
(d) Assertion (A) is wrong but the Reason (R) is correct.
1. Assertion (A): We feel more comfortable carrying a bag with broad straps as compared to bag of the same weight with narrow straps.
Reason (R): Broad straps reduce the pressure exerted by the bag on our shoulders as compared to narrow straps.
Answer:
(a) Assertion (A) and Reason (R) both are correct and reason is correct explanation for assertion.
2. Assertion (A): The base of the dam is kept narrower than the top to keep the dam strong to hold a huge amount of water.
Reason (R): The water stored in the dam exerts pressure horizontally on the side walls of the dam and vertically on the floor due to the height of the water level. The pressure that acts horizontally is very large near its bottom.
Answer:
(d) Assertion (A) is wrong but the Reason (R) is correct.
Fill in the blanks
1. Force acting on a area is called …………
Answer:
pressure
2. The pressure exerted by a liquid ………… with depth.
Answer:
increases
3. Overhead water tanks are placed high to increase water ………… in the pipes.
Answer:
pressure
4. 1 Pascal (Pa) equals 1 ………… per square metre.
Answer:
Newton
5. Liquid exert pressure at the bottom and also on the ………… of a container.
Answer:
walls
True or False
1. The pressure exerted by a liquid depends on the area of a base of its container.|
Answer:
False
2. A drinking straw works on the pressure exerted by the liquid filled in a soft drink bottle in which it is placed.
Answer:
False
3. Atmospheric pressure decreases with altitude.
Answer:
True
4. A liquid exerts presure either in downward direction or sideways, but not in upward direction.
Answer:
False
5. When the height of the liquid column in a tall jar is doubled, the pressure at the bottom also gets doubled.
Answer:
True