WBBSE Solutions For Class 6 Geography Chapter 4 Rotation Of The Earth Topic A Rotation Of The Earth And Day Night

Class 6 Geography WBBSE Chapter 4 Rotation of the Earth Chapter Synopsis

1. Since the Earth spins in a west-to-east direction, the Sun seems to rise in the east and set in the west every day. This is known as the Sun’s apparent daily motion or movement.

2. The Earth spins on its axis tilted at an angle of 66V20 to the orbital plane in a west-to-east direction. This is known as the rotation of the Earth.

3. The circle that divides the Earth into a lit half and a dark half is called the circle of illumination or shadow circle. The lighted half of the Earth experiences day and the dark half experiences night.

4. The transitional time immediately before sunrise is called dawn and that immediately after sunset and before the evening is called dusk.

5. The Earth pulls everything towards its center. This tension is known as gravity.

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6. The International Date Line is an imaginary line that follows the 180° longitude mostly, except in a few places.

7. When the Sun remains overhead on a particular meridian, it is 12 noon at all places on the same meridian. That is why lines of longitudes are known as meridians.

8. The time of a place that is calculated from 12 noon is known as the local time of that place.

9. A meridian that passes through the middle of a country is considered as the standard meridian of that country. And the local time of that meridian is considered the standard time of that country.

10. The local time of 82°30 ‘E meridian has been taken as the Indian Standard Time (1ST).

11. Ante Meridian (am) is the period of time between 12 midnight and 12 noon. Similarly, the time between 12 noon and before 12 midnight is called Post Meridian (pm)

Class 6 Geography WBBSE Chapter 4 Rotation of the Earth Topic A Rotation of the Earth and Day-Night Analytical Type Questions

Question 1. What do you mean by the rotation of the Earth?
Answer:

Rotation of the Earth:

The motion by which the Earth spins on its axis at an angle of 661A° with the orbital plane in a west-to-east direction is called Earth’s rotation.

Characteristics: Some important characteristics of Earth’s rotation are:

1. Direction of motion: The Earth rotates from west to east.

2. Speed: The speed of Earth’s rotation is highest at the Equator with a speed of 1650km/hour and almost zero at the Poles.

3. Time period: The Earth takes 23 hours 56 minutes 4 seconds for a single rotation.

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4. Effects: The effects of Earth’s rotation are:

1. The cycle of day and night,
2. The occurrence of tides,
3. Direction change of ocean currents and wind in each hemisphere,
4. Origin and maintenance of life on Earth, etc.

 

 

Question 2. How do you prove that the Earth has a rotational movement?
Answer:

Earth has a rotational movement:

The rotational movement of the Earth can be proven by various instances as follows:

Formation of day and night: It is because of the rotational movement of the Earth that any place on the Earth faces the Sun once a day.

Without rotation, one side of the Earth would have eternal day and the other side would have eternal night.

Sunrise and sunset: Each and every place on the Earth’s surface experiences sunrise and sunset once a day because of the rotational movement of the Earth.

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Law of gravity: According to Newton’s Law of Gravity, the Sun being of much larger size and with greater mass cannot rotate around the Earth.

On the contrary, it is the Earth that rotates and revolves at the same time around the Sun.

Rotational movement of other planets: All the other planets of the solar system like Venus, Mercury,

Mars rotates on their axes. As the Earth is a planet of the same solar system, it cannot be an exception.

The oblate spheroid shape of the Earth: The Earth has been rotating since it was formed. Thus, it has become flattened at the Poles and bulged out at the Equator. Without rotational movement, the Earth would not have taken this shape.

Satellite images: From satellite images, it can be clearly seen that the Earth is continuously rotating around the Sun.

Question 3. Discuss the effects of the earth’s Rotation.
Answer:

The effects of Earth’s rotation are as follows:

Formation of day and night: It is because of the rotational movement of the Earth that any place on it faces the Sun once a day. The area facing the Sun experiences day, and the opposite side experiences night.

Sunrise and sunset: The Sun seems to rise in the east and set in the west as a result of its rotation from west to east.

Determination of time: The Earth takes 24 hours or 1 day to complete one rotation. Days and dates are calculated with respect to each passing 24 hours. Time is determined by dividing 1 hour into 60 minutes and 1 minute into 60 seconds.

Life on Earth: There will be an eternal day on the side facing the Sun and an eternal night on the side away from the Sun if the Earth stops rotating.

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Moreover, the temperature would be very high on the side experiencing day and very low on the side experiencing night. Thus, life on Earth as we know exists only because of the Earth’s rotational movement.

High tide and low tide: High tide and low tide of oceans are also caused by the rotational movement of the Earth.

While rotating, the side that faces the Sun and the Moon and the side exactly opposite to it experience high tide. The other two ends of the Earth experience low tide simultaneously.

The oblate spheroid shape of the Earth: While rotating on its axis, the Earth exerts a centrifugal force. As a result, the shape of the Earth has become like an oblate spheroid.

Question 4. What are the different phases of the day created by the rotation of the Earth?
Answer:

The phases of the day created by the rotation of the Earth are as follows:

Dawn and morning: The side of the Earth that faces the Sun and comes into brightness from darkness experiences morning. Just before the Sun actually rises, the sunrays that get diffused by dust particles, water vapor, clouds, etc.

In The sky and create a condition of mellow light. This transitional time period of diffused sunlight is known as dawn.

Midday and midnight When the Sun is exactly overhead at a particular place, it is 12 noon at that place.

The exact opposite situation occurs at midnight, which is at the antipode of that place where it is noon.

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Evening and dusk: The side of the Earth that faces away from the Sun and enter into darkness from brightness experiences evening.

Just after the Sun actually sets, the sun rays get diffused by dust particles, water vapor, clouds, etc in the sky and create a condition when the sunlight starts fading. This transitional time period of diffused sunlight is known as dusk.

Chapter 4 Rotation of the Earth Topic A Rotation of the Earth and Day-Night Short Analytical Type Questions

 

Question 1. What is the apparent daily movement of the Sun?
Answer:

Daily movement of the Sun:

Every day, the Sun rises in the east and sets in the west—this is called the apparent daily or diurnal motion of the Sun.

Though the Sun seems to be moving in relation to the Earth, it is actually the Earth’s motion from west to east that causes this phenomenon.

That is why, it is called the apparent motion of the Sun This is somewhat like when we are on a moving train, it is the stationary features of the landscape outside that seem to be moving past us.

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Question 2. Is the speed of rotation of the Earth equal everywhere? Explain.
Answer:

The speed of rotation of the Earth equal everywhere:

The Earth is shaped like an oblate-spheroid, flattened at the Poles and bulging out at the Equator.

As a result, the circumference of the Earth is highest at the Equator and it decreases gradually towards the Poles.

This means that when the Earth spins around its axis, it does so at different speeds at different latitudes.

The speed of rotation is highest at the Equator, 1650 km/ hour, as the circumference of the Earth is highest here and almost 0 km/hour at the Poles.

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Question 3. Why does the speed of rotation gradually decrease from the Equator toward the Poles?
Answer:

The speed of rotation gradually decrease from the Equator toward the Poles:

If a spherical object is flattened at the top and bulged out in the middle, then it will not rotate with the same speed if it is forced to rotate on a stick.

The same thing happens in the case of the Earth. The Earth has a flattened top and bottom and a bulging-out equatorial region. But the time of rotation is the same, i.e. 24 hours.

So, the Earth requires a higher speed to cover the equatorial circumference than to cover the circumference at the Poles, because the polar circumference is smaller.

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Thus, the rotational speed of the Earth which is 1650 km/hour at the Equator reduces to 0 km/hour at the Poles.

Question 4. Write a short note on the circle of illumination.
Answer:

Circle of illumination:

The circle that divides the Earth into a lit half and a dark half is the circle of illumination or shadow circle. The lit half of the Earth experiences day and the dark-half experiences evening and night.

The places on Earth through which the shadow circle passes do not see the Sun at a particular point time of the day.

But they receive the diffused rays of the Sun. The transitional time of diffused sunlight before sunrise is called dawn and that after sunset is called twilight.

Characteristics: Some characteristics of the circle of illumination are—

Due to the spherical shape of the Earth, the circle of illumination is circular in shape.

The shadow circle is not constant. Due to the rotation of the Earth, the places through which it passes change continuously.

Question 5. What will happen if the Earth stops rotating?
Answer:

If the Earth stops rotating, then—

1. The side facing the Sun will become tremendously hot and the opposite side will become too cold.
2. There will be an eternal day on the bright side and an eternal night on the dark side of the Earth.
3. Due to these extreme temperature conditions life on Earth would cease to exist.

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Question 6. What are the differences between the apparent daily motion and the apparent annual motion of the sun?
Answer:

The differences between the apparent daily motion and the apparent annual motion are as follows—

 

Question 7. How is time related to the rotation of the Earth?
Answer:

Time related to the rotation of the Earth:

The concept of time is completely dependent on the rotation of the Earth. One complete rotation of the Earth takes 24 hours.

These 24 hours, if divided into 24 divisions, each division is taken to be an hour. One hour can be divided into 60 minutes and one minute can be divided into 60 seconds.

Thus the calculation of minutes and seconds is possible because of the rotation of the Earth.

Chapter 4 Rotation of the Earth Topic A Rotation of the Earth and Day-Night Short Answer Type Questions

Question 1. What is meant by Earth’s rotation?
Answer:

Earth’s rotation:

The Earth spins on its axis tilted at an angle of 6634° to its orbital plane, from west to east. This movement is called Earth’s rotation. The Earth takes 23 hours 56 minutes and 4 seconds to complete one rotation.

Question 2. Calculate how far the Earth rotates in an hour.
Answer:

Earth rotates in an hour:

The Earth takes almost 24 hours to complete one rotation and the circumference of the Earth is about 40,000 km. That means, the Earth travels 40,000 km in 24 hours.

Then, the Earth travels (40,000 + 24) km = 1,666.66 km or 1,667 km (approx) in one hour.

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Question 3. Why is the speed of the Earth’s rotation almost zero at the Poles?
Answer:

The speed of the Earth’s rotation almost zero at the Poles:

The speed of the Earth’s rotation depends on its circumference. Since the Poles are mere dots, their circumference is 0.

As a result, there can be no motion and no speed of the Earth’s rotation felt at the Poles.

Question 4. Why is the Sun or any other star was seen first in the eastern sky?
Answer:

The Earth rotates from the west to the east on its axis. Thus, we see the Sun or any other star first in the eastern sky.

Question 5. What is meant by dawn?
Answer:

Dawn:

Before sunrise, the sunrays that are diffused by dust particles, water vapor, clouds, etc create a condition of mellow light. This transitional time period of diffused sunlight is known as dawn.

Question 6. What is meant by dusk or twilight?
Answer:

Dusk or twilight:

After sunset, the sunrays get diffused by dust particles, water vapor, clouds, etc. in the sky. As a result, the sky appears yellowish-orange in color. This transitional time period of diffused sunlight is known as dusk.

Question 7. When is our shadow the longest and when is it the shortest?
Answer:

Our shadow is the longest right after sunrise (early morning) and right before sunset (early evening). Our shadow is the shortest when the Sun is directly overhead at noon.

Question 8. Why don’t we fall off even if the Earth is rotating?
Answer:

The Earth’s rotational movement from west to east should have made us unstable in our positions.

But the gravitational pull of the Earth holds us back. This is the reason why we do not fall off even though the Earth is in constant rotation.

WB Class 6 Geography Chapter 4 Rotation Of The Earth Topic A Rotation Of The Earth And Day-Night Multiple Choice Questions

Question 1. The sun rises in the east and sets in the west every day; this is-

1. The sun’s apparent daily motion
2. The earth’s apparent daily motion
3. The sun’s apparent yearly motion

Answer: 1. The sun’s apparent daily motion

Question 2. The fact that the sun and not the earth is at the center of the solar system was first proved by—

1. Ptolemy
2. Eratosthenes
3. Copernicus

Answer: 3. Copernicus

Question 3. Copernicus was a—

1. Greek astronomer
2. Roman astronomer
3. Polish astronomer

Answer: 3. Polish astronomer

Question 4. The earth spins on its axis in a west-to-east direction. This is called its—

1. Rotation
2. Revolution
3. Apparent motion

Answer: 1. Rotation

Question 5. The earth rotates from—

1. East to west
2. West to east
3. North to south

Answer: 2. West to east

Question 6. The speed of rotation of the earth is maximum at the—

1. Tropic of cancer
2. Arctic circle
3. Equator
4. South pole

Answer: 3. Equator

Question 7. At the equator, the earth rotates at a speed of—

1. 1,650 Km/hour
2. 1,550 Km/hour
3. 1,450 Km/hour

Answer: 1. 1,650 Km/hour

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Question 8. The circle that divides the day from night on the globe is called—

1. The equator
2. The great circle
3. The circle of illumination

Answer: 3. The circle of illumination

Question 9. The reason why we do not fall off the earth though it is in constant motion is its—

1. Gravitational force
2. Centrifugal force
3. Centripetal force

Answer: 1. Gravitational force

Question 10. The time of day when shadows are longest is—

1. Dawn
2. Noon
3. Afternoon

Answer: 3. Afternoon

Question 11. If we divide one hour into 60 equal parts, we get—

1. 1 Minute
2. 1 Second
3. 1 Microsecond

Answer: 1. 1 Minute

Chapter 4 Rotation Of The Earth Topic A Rotation Of The Earth And Day-Night Fill In The Blanks

Question 1. The fact that the Earth revolves around the Sun was first stated by__________
Answer: Copernicus

Question 2. The Earth rotates on its axis at an angle of __________to its orbital plane.
Answer: 66½º

Question 3. The time taken by the Earth to complete one rotation around the Sun is almost 23 hours__________
Answer: 56 minutes 4 seconds

Question 4. The length of the lines of latitude start__________ as we move towards the Poles.
Answer: Decreasing

Question 5. The circular line that divides the day from night on the Earth is called the__________
Answer: Circle of illumination

Question 6. The mellow light time period that exists before sunrise is called__________
Answer: Dawn

Question 7. The diffused light time period that exists when the Sun sets is called__________
Answer: Dusk/twilight

Question 8. The first scientist to talk about the existence of gravitational force was__________
Answer: Newton

Question 9. The Sun is directly overhead at__________
Answer: Noon

Question 10. Shadows are shortest at__________
Answer: Noon

Question 11. One hour is equal to__________ seconds
Answer: 3,600

Chapter 4 Rotation Of The Earth Topic A Rotation Of The Earth And Day-Night Write True Or False

Question 1. The Earth’s axis is at an angle of 6634° to its orbital plane.
Answer: True

Question 2. The Earth rotates on its axis from east to west.
Answer: False

Question 3. The time right after sunset is called dusk.
Answer: True

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Question 4. The speed of rotation of the Earth is highest in the Tropics.
Answer: False

Question 5. It was Copernicus, who proved that the Sun is at the center of the solar system.
Answer: True

Question 6. The circumference of the Earth at the Equator is almost 40,000 km.
Answer: True

Question 7. The speed of the Earth’s revolution around the Sun is used to determine time.
Answer: False

Question 8. The speed of rotation of the Earth does not change with a change in latitude.
Answer: False

Question 9. At the Equator, the Earth’s speed of rotation is almost 1,650 km/hour.
Answer: True

Question 10. Our shadows are the shortest at the time of sunrise.
Answer: False

Question 11. The Earth has been rotating on its axis ever since it was formed.
Answer: True

Question 12. Fill The path along which the Earth revolves around the Sun is called its focus.
Answer: True

Question 13. The circle of illumination divides the Earth into a dark half and a lit half.
Answer: True

Question 14. We will not have the cycle of day and night if the Earth stops rotating around the Sun.
Answer: True

Question 15. One solar day is equal to 23 hours 56 minutes 4 seconds.
Answer: True

Question 16 When it is dawn at a place, it is dusk at its antipode.
Answer: True

Chapter 4 Rotation Of The Earth Topic A Rotation Of The Earth And Day-Night Match The columns

 

Answer: 1-B,2-C,3-D,4-A

Chapter 4 Rotation Of The Earth Topic A Rotation Of The Earth And Day-Night Answer In One Or Two Words

 

Question 1. Rising in the east, being directly overhead at noon, and setting in the west every day— what is this motion of the Sun called?
Answer: Apparent daily motion of the Sun.

Question 2. What is the Earth’s rotation speed in the Tropics?
Answer: 1,550 km/hour.

Question 3. Name the place on the Earth where the speed of rotation will be lowest.
Answer: Poles.

Question 4. What is the rotation speed of the Earth at the Poles?
Answer: Almost zero.

Question 5. If it is a day where you are, and you cross the circle of illumination, what part of the day will it be?
Answer: Evening.

Question 6. If you cross the dark half of the Earth and cross the circle of illumination, what part of the day will it be?
Answer: Dawn.

Question 7. What is the diffused light time period after sunset called?
Answer: Dusk or twilight.