Class-7 Science Chapter-8 Winds, Storms and Cyclones, Additional Exercises in line with NCERT book / CBSE Syllabus

Chapter 8

Winds, Storms and Cyclones

Exercises from textbook

Additional Exercises

Activities/Projects

Additional Exercises

Choose the correct answer:

(1)    The leaves of trees flutter when the wind is blowing. This is due to

a.       Air pressure (√)

b.       Air vacuum

c.        Plant force

d.       Transpiration

(2)    Wind currents are generated due to

a.       Uneven heating between the equator and the poles

b.       Uneven heating of land and water .

c.        Both a and b (√)

d.       None of the above

(3)    In ____, wind flows from the land to the oceans.

a.       Summer

b.       Winter (√)

c.        All seasons

d.       Both a and b

(4)    Direction of wind flow is determined by the

a.       rotation of earth (√)

b.       revolution of earth

c.        Temperature of earth

d.       Movement of clouds

(5)    Which of these situations create disaster and pose threat to humans, animals and plant life?

a.       Thunderstorms

b.       Cyclones

c.        Monsoon

d.       Both a and b (√)

(6)    Which of these factors contributes to the development of cyclones?

a.       Wind direction

b.       Wind speed

c.        Temperature and Humidity

d.       All the above (√)

Differentiate between:

Cyclone and Tornado

Cyclone	Tornado
Cyclone is large-scale air mass that circulates around a center of low atmospheric pressure.	Tornado is a rotating column of air accompanied by a funnel-shaped cloud that progresses in a narrow path over the land
Cyclone has a very large diameter.	Tornado has a small diameter.
Made of multiple convective storms.	Made of single convective storm.
It is an oceanic phenomenon, they die over land masses.	It is a land phenomenon.

Match the column:

A	B
Air around us	causes wind movements
Air expands	monitor cyclones
Warm air	exerts pressure
Uneven heating on earth	rises up
Satellites and radars	on heating

Ans

A	B
Air around us	exerts pressure
Air expands	on heating
Warm air	rises up
Uneven heating on earth	causes wind movements
Satellites and radars	monitor cyclones

State whether the following statements are True or False:

1-    Moving air is called wind.   (True)

2-    The greater the difference in air pressure, faster the air moves. (True)

3-    Warm air rises up. (True)

4-    A person can easily overcome the water waves produced by the cyclone. (False)

5-    Cyclone increases the fertility of soil. (False)

6-    The west coastline of India is less vulnerable to cyclonic storms both in terms of intensity and frequency of the cyclones. (True)

Give one word for the following:

(1)   The wind that carries water and it rains. – Monsoon

(2)   The coastline of India which is more vulnerable to cyclones.- East coast

(3)   A dark funnel shaped cloud that reaches from the sky to the ground. – Tornado

(4)   The instrument which is used to measure the speed of wind. - Anemometer

Encircle the Odd one:

(1)   Cyclone, Hurricane, Tornado, Typhoon

(2)   Wind sock, Rain gauge, Wind vane, Anemometer

Fill in the blanks:

(1)   The moving air is called wind.

(2)   Air exerts pressure.

(3)   High speed winds are accompanied by reduced air pressure.

(4)   Air moves from the region where the air pressure is high to the region where the pressure is low.

(5)   On heating air expands and occupies more space.

(6)   The winds from oceans carry water and bring rain.

(7)   Using satellites and radars, a cyclone alert can be issued 48 hours in advance of any expected storm.

Answer the following questions:

 Q. If you are in a boat, is it easier to row it if there is wind coming from behind you?

Ans- Yes, it is easier to row a boat if there is wind coming from behind us because the wind coming from behind exerts it's pressure in the direction of movement and makes it easy.

Q. Take a soft plastic bottle. Fill it with hot water. Empty the bottle and immediately cap it tightly. Place the bottle under running water. What happens to the bottle?

Ans- The bottle gets distorted. As the water is poured over the bottle, some steam in the bottle gets condensed into water reducing the amount of air inside the bottle. As a result, the pressure of air inside the bottle becomes less than the pressure exerted by the air from outside leading to distortion of bottle.

Q. When you blow in the space between the two balloons filled with little water and air, tied 8-10 cm apart, they move apart. Why?

Ans- The balloons move towards each other when we blow in the space in between them because the pressure of air between the balloons reduces due to high speed. The pressure outside the balloons pushes them towards each other.

Q. Observe the adjoining figure and answer the following questions.

1)What makes the balloon inflates when the booking tube is places in hot water?

2) Why is the same balloon dedicated when the tube is jeet in cold water?

Ans- When the booking tube is places in hot water, the air inside the tube expands due to the effect of heat. The is makes the balloon inflated.

When the same tube is kept in cold water, the balloon is deflated because volume of air inside the tube decreases due to low temperature.

Q. How are monsoon wind generated?

Ans- In summer, the land near the equator warms up faster and most of the time the temperature of the land is higher than that of water in the oceans.

The air over the land gets heated and rises up. This causes the winds to flow from oceans towards the land. These are the monsoon wind that carry water and it rains.

Q. How does uneven heating between the equator and the pole generate wind currents?

Ans- The regions near the equator get maximum heat from the sun. The air in these regions gets warm. The warm air rises, and the cooler air from the regions in higher latitude belt on either side of the equator moves in. These winds blow from the north and the south towards the equator. In this way, wind circulation is set up from the poles to the warmer latitudes.

Q. What do you meaning by thunderstorm?

In hot humid and tropical areas (like India), the rising temperature produces string upward rising winds. These winds carry water droplets upwards, where they freeze, and fall down again. The swift movement of the falling water droplets along with the rising air create lightning and sound. It is this event that is called thunderstorm.

Q. What is Tornado?

Ans- A tornado is a dark funnel shaped cloud that reaches from the sky to the ground. Tornadoes may form within cyclones.

A violet tornado can travel at speed of about 300 km/h.

Give reason. Why?

Q. Roofs of houses are lifted up and blown away in high-speed wind. Why?

Ans- High speed winds are accompanied by reduced air pressure. If the roof of house is week, the pressure inside the house (below roof) becomes more than the pressure above the roof. Therefore roofs of houses are lifted up and blown away in high speed wind.

Q. A bicycle tube overfilled with air may burst. Why?

Ans- Overfilled air inside the tube exerts pressure on the casing and eventually the tyre gets burst.

Q. You find difficult to ride a bicycle opposite to direction of wind.

Ans- We find it difficult to ride a bicycle opposite to the direction of wind because the blowing wind exerts pressure on us in the direction opposite to the direction of movement.

Q. You find it difficult to force blow the ball of crumpled paper in an empty bottle?

Ans- When we blow into the mouth of the bottle, air near the mouth has higher speed. This decreases the pressure there. The air pressure inside the bottle is higher than near the mouth so air inside the bottle pushes the ball out and we find it difficult to force the paper ball into the bottle.

Flow Chart

The following flow chart helps to understand the phenomenon that leads to the formation of clouds and falling of rain and creation of storms and cyclone.

Exercises from Textbook

Q. Fill the missing word in the blank spaces in the following statement

a)    Wind is moving air.

b)    Winds are generated due to uneven heating on the earth.

c)    Near the earth’s surface, hot air rises up whereas cold air comes down.

d)    Air moves from a region of high pressure to a region of low pressure.

Q. Suggest two methods to find out wind direction at a given place.

Ans- Following are two ways to find out wind direction at a given place:

(1)   Hold a corner of handkerchief at an arm distance from your body. The direction in which the handkerchief blows is the direction of wind.

(2) Hold a paper strip in hand and observe the direction in which it moves to know the direction of wind.

Q. State two experiences that made you think that air exerts pressure.

Ans- Following are two experiences that make us think that air exerts pressure:

(1)   Curtains at the window keep moving because the air exerts pressure.

(2)   On the top of a hillock, we see our hairs and clothes moving in the direction of wind flow. This shows that air exerts pressure.

Q. You want to buy a house. Would you like to buy a house having windows but no ventilators? Explain your answer.

Ans- In our house, cold and fresh air enters through windows while the warm and impure air rises up and goes out through ventilators. Therefore, it won’t be a wise decision to buy a house having windows but no ventilators.

Q. Explain why holes are made in hanging banners and hoardings.

Ans- Holes are made in hanging banners and hoardings so that air can easily pass through these holes and the banners/hoardings can be saved from getting damaged due to air pressure.

Q. How will you help your neighbours in case cyclone approaches your village / town?

Ans- Following are the ways by which we can help neighbours in case cyclone approaches our village.

1-    Help neighbours move to cyclone shelter or other safe area.

2-    Help them shift animals and other necessary goods to safer place.

3-    Making arrangement for food and clean drinking water.

4-    Call the emergency services like police, fire brigade and medical centres when required.

5-    Not ignoring the warnings given on TV channels and news papers.

6-    Avoiding drive on roads through standing water, as the flood may have damaged the roads.

Q. What planning is required in advance to deal with the situation created by a cyclone?

Ans- Planning required in advance to deal with the situations created by a cyclone can be mentioned in following points:

(1)   Good radars and satellite system in place to get advance warning.

(2)   Preparing cyclone-shelters to be used in case of emergency.

(3)   Keeping the phone numbers of emergency services like police, fire brigade and medical centres handy and using them when needed.

(4)   Keeping ample stock of food and drinking water.

(5)   Keeping emergency medicines in a handy kit.

 Q. Which one of the following place is unlikely to be affected by a cyclone.

(i)            Chennai

(ii)           Mangaluru (mangalore)

(iii)          Amritsar (√)

(iv)          Puri

Ans- Amritsar

Q. Which of the statemnets given below is correct?

1-    In winter the winds flow from the land to the ocean. (√)

2-    In summer the winds flow from the the land towards the ocean.

3-    A cyclone is formed by a very high-pressure system with very high-speed winds revolving around it.

4-    The coastline of India is not vulnerable to cyclones.

Extended learning - activities and projects

(1)   Take two plastic bottles of the same size. Stretch one balloon on the neck of each bottle. Keep one bottle in the sun and the other in the shade. Record your observations.

(2)   You can make your own anemometer.

Collect the following items.

4 paper cups (used for icecream)

2 strips of cardboard (20 cm long and 2 cm wide)

gum

stepper

a sketch pen

sharpened pencil with eraser at one end

Take a scale; draw crosses on the cupboard strips as shown in the fig below. This will give you the centers of the strips.

Fix the strips at the centre, putting one over the other so that they make a plus (+) sign. Now fix the cups at the ends of the strips. Colour the outer surface of one cup with a market or a sketch pen. All the 4 cups should face in the same direction.

Push a pin through the centre of the strips and attach the strips and the cups to the eraser of the pencil. Check that the strips rotate freely when you blow on the cups. Your anemometer is ready. Counting the number of rotations per minute will give you an estimate of the speed of the wind. To observe the changes in the wind speed, use it at different places and different times of the day.

If you do not have a pencil with attached eraser you can use the tip of a ball pen . The only condition is that the strips should rotate freely.

Remember that this anemometer will indicate only speed changes. It will not give you the actual wind speed.

(3)   Collect articles and photographs from newspapers and magazines storms and cyclones. Make a story on the basis of what you learnt in this chapter and the matter collected by you.

(4)   Suppose you are a member of a committee which is responsible for creating Development Plan of a coastal state. A short speech indicating the measures to be taken to reduce the suffering of people caused by cyclones.

(5)   Interview eyewitnesses to collect the annual experience of people affected by a cyclone.

(6)   Take an aluminium tube about 15 cm long and 12 1.5 CM in diameter. Cut slice of a medium sized potato about 2 cm thick. Insert the tube in the slice, press it and rotate it to two three times. Remove the tube. You will find a piece of potato paste in the tube like a piston head. The same process with the other end of the tube. Now you have the tube with both ends closed by potato pieces with an air column in between. Take a pencil with one and unsharpened. Please this end at one of the pieces of potato. Observe what happens. The activity shows rather tematica Lee how increased air pressure can push things.

Caution:  When you perform this activity make sure that nobody is standing in front of the tube.

You can read more on the related topics on the following website:

http://www.imd.gov.in

Did you know?

A Bolt of lightning Travels at a speed of more than 400000 kilometer / hour. It can heat the air around it to a temperature, which is more than 4 times the temperature of the surface of the Sun. That is what makes lightning so dangerous.

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