Kerala Syllabus STD 8 Social Science: Chapter 03 Movements of the Earth: Rotation and Revolution - Questions and Answers | Teaching Manual | Teachers Handbook
ഈ ബ്ലോഗ് അഡ്മിൻറെ രേഖാമൂലമുള്ള അനുമതിയില്ലാതെ ഈ ബ്ലോഗിൽ നൽകിയിരിക്കുന്ന ചോദ്യോത്തരങ്ങൾ, ഇതേരീതിയിലോ പി.ഡി.എഫ് രൂപത്തിലോ, മറ്റേതെങ്കിലും ഡിജിറ്റലോ, പ്രിന്റഡ് ഉൾപ്പെടെയുള്ള ഏതെങ്കിലും രൂപങ്ങളിലേക്കോ മാറ്റി മറ്റൊരു വെബ്സൈറ്റിലോ, ബ്ലോഗിലോ, യുട്യൂബ്, സോഷ്യൽ മീഡിയാ ഗ്രൂപ്പുകളിലോ ഉൾപ്പെടെ ഒരിടത്തും പ്രചരിപ്പിക്കാൻ പാടില്ലാത്തതാകുന്നു.
Chapter 03: Movements of the Earth: Rotation and Revolution - Questions and Answers
♦ Why do we feel that the sun rises in the east and sets in the west?
The direction of rotation of the Earth is from the west to the east. That is why we feel that the sun rises in the east and sets in the west.
♦ Look at Figure 3.3 (Textbook Page 44) and answer the following questions related to rotation.
| • direction of the Earth’s rotation | From the west to the east |
| • tilt of the Earth's axis | 23.5° |
♦ What are the two main effects of the rotation of the Earth?
• Day and night
• Coriolis effect
♦ What is called the Circle of Illumination?
The imaginary line that demarcates day and night on the Earth is called the Circle of Illumination.
♦ What is the time taken for the Earth to complete one rotation?
24 hours (23 hours 56 minutes 4 seconds)
♦ What is known as the Coriolis Force? What is called the Coriolis Effect?
Due to rotation, freely moving bodies on the Earth's surface get deflected in their direction. The force responsible for this deflection is known as Coriolis Force and the deflection in direction is called Coriolis Effect.
♦ Define Ferrel's law
Admiral Ferrel discovered that due to the Coriolis Effect,ocean currents and winds change their direction in the northern hemisphere to the right and in the southern hemisphere to the left. This is known as Ferrel's law.
♦ Some facts related to rotation are given below. Complete the table by finding out the reasons behind these facts
| • The Sun rises in the east and sets in the west. | The direction of rotation of the Earth is from the west to the east |
| • Freely moving bodies get deflected in their direction in both hemispheres | Coriolis Force |
♦ What is known as Revolution?
While rotating on its axis, the Earth revolves around the Sun in a fixed orbit. This is known as Revolution.
♦ What is the time taken to complete one revolution in the elliptical orbit?
365¼ days
♦ What is a leap year?
The year which has 366 days.
Eg:2024,2028,2032,2036
♦ Difference between Perihelion and Aphelion?
• The day on which the Earth comes closest to the Sun during revolution (147 million kilometres) is known as Perihelion. This happens in the month of January (around 3rd January).
• The distance between the Sun and the Earth will be at a maximum (152 million kilometres) in the month of July (around 4th July). This is called Aphelion
♦ What is the speed of revolution of the Earth in km per second?
The speed of revolution of the Earth is around 30 km per second.
♦ What are the effects of the difference in the distance between the Earth and the Sun?
The distance between the Earth and the Sun causes a difference in gravitational force and the speed of revolution
♦ What is the apparent movement of the Sun?
Since the tilt of the earth’s axis is maintained at an angle of 23½ degree throughout the revolution, the Sun’s apparent position moves northward and southward between the Tropic of Cancer and the Tropic of Capricorn. This apparent shift in the Sun’s position is called the apparent movement of the Sun.
♦ Effects of the apparent movement of the Sun
The duration of day and night changes
♦ On which latitude do the Sun’s rays fall vertically?
Zero degree latitude(Equator)
♦ On which days does this happen?
21st March and 23rd September
♦ What are called equinoxes? Classify equinoxes and write a note.
During the Revolution, on 21st March and 23rd September, the sun’s rays fall vertically on the equator. The duration of day and night will be equal on both hemispheres on these days. These days are called equinoxes.
21st March is known as Spring Equinox and 23rd September is Autumnal Equinox.
♦ Look at the figure
Towards north from the Equator to the Tropic of Cancer
♦ On which latitude do the sun’s rays fall vertically on 21st June?
Tropic of cancer
♦ Write a short note about the Summer Solstice.
In the northern hemisphere, the Sun’s apparent position shifts towards north from the Equator to the Tropic of Cancer from 21st March to 21st June. As a result of this on 21st June, the northern hemisphere experiences the longest day and the shortest night. This day is known as summer solstice.
♦ The table showing the length of day in different latitudes on the summer solstice (June 21) is given below.
| Latitude | Length of day |
|---|---|
| 90° North | 24 hours |
| 66½° North | 24 hours |
| 23½° North | 13 hours 27 minutes |
| 0° North | 12 hours |
| 23½° South | 10 hours 33 minutes |
| 66½° South | Nil |
| 90° South | Nil |
♦ What are the changes that happen to the length of day in the southern hemisphere on the summer solstice (June 21)?
• Moves southward in the southern hemisphere, the length of the day gradually decreases.
• From the Antarctic Circle to the South Pole, there is no daylight.
♦ What will be the duration of the night in the southern polar regions when there is daylight for six months in the northern polar regions?
For six months, from June to March, the Sun's apparent position will be in the northern hemisphere. During this period, in the southern polar region, there will be continuous darkness for six months.
♦ Look at the figure
♦ In which direction does the Sun’s apparent position shift from 23rd September onwards?
Southward Direction
♦ On which latitude do the Sun's rays fall vertically on 22nd December?
Tropic of Capricorn
♦ Write a short note about the Winter Solstice.
In the southern hemisphere the Sun’s apparent position shifts from the equator to the Tropic of Capricorn during the period from 23rd September to 22nd December. As a result of this, on 22nd December, the southern hemisphere experiences the longest day and the shortest night. This day is known as the Winter Solstice.
♦ What are the changes that happen to the length of day in the northern hemisphere on the winter solstice (December 22)?
• Moves northward in the northern hemisphere, the length of the day gradually decreases.
• From the Arctic Circle to the North Pole, there is no daylight.
♦ What will be the duration of the night in the northern polar regions when there is daylight for six months in the southern polar regions?
For six months, from September to March, the Sun's apparent position will be in the southern hemisphere. During this period, in the northern polar region, there will
be continuous darkness for six months.
♦ The table shows the duration of daytime in different latitudes on the winter solstice (December 22).
| Latitude | Length of day |
|---|---|
| 90° North | Nil |
| 66½° North | Nil |
| 23½° North | 10 hours 33 minutes |
| 0° North | 12 hours |
| 23½° South | 13 hours 27 minutes |
| 66½° South | 24 hours |
| 90° South | 24 hours |
♦ Explain what is Uttarayanam and Dakshinayanam?
• Following the winter solstice (December 22) the apparent movement of the Sun from Tropic of Capricorn (23½° South) to Tropic of Cancer (23½0 North) is known as the apparent movement of the Sun towards North (Uttarayanam).
• The shift in the apparent position of the Sun after the Summer Solstice (June 21) from the Tropic of Cancer (23½° North) to Tropic of Capricorn (23½0 South) is known as the apparent movement of the Sun towards South (Dakshinayanam).
♦ Complete the table.
♦ What are seasons? Reason for the occurrence of the seasons?
• Due to the apparent shift in the position of the Sun, different places experience specific weather patterns. These patterns are known as seasons.
• The revolution of the Earth and variations in the availability of solar energy is the reasons for the occurrence of the seasons.
♦ What is called seasonal change?
The occurrence of spring, summer, autumn and winter in a cyclical manner during a year is called seasonal change.
♦ Make a table on different seasons and their characteristics
| Seasons | Characteristics |
|---|---|
| • Spring | • plants bloom and produce fruits • During this period duration of daytime gradually increases |
| • Summer | • high atmospheric temperature • generally longer days |
| • Autumn | • trees shed their leaves before the arrival of winter • during this period duration of daytime gradually decreases |
| • Winter | • low atmospheric temperature • snowfall • generally longer nights |
♦ Observe the table about the different seasons in northern and southern hemispheres and write the answers for the questions given below.
• What change happens to the apparent movement of the Sun when it is summer season in the northern hemisphere?
The sun's apparent position shifts from the Tropic of Cancer to the equator
• What will the season be in the northern hemisphere when it is autumn in the southern hemisphere?
Spring is experienced in the Northern Hemisphere
• Which season is experienced in the southern hemisphere from 23rd September to 22nd December?
Spring is experienced in the Southern Hemisphere
• Name the season in the southern hemisphere when the Sun's apparent position shifts from the Tropic of Capricorn to the equator.
Summer is experienced in the Northern Hemisphere
♦ Classify the following countries under the northern hemisphere and the southern hemisphere
Australia, India, Sri Lanka, South Africa, Japan, Argentina
| northern hemisphere | southern hemisphere |
|---|---|
| • India • Sri Lanka • Japan | • Australia • South Africa • Argentina |
♦ Complete the following table related to time calculation
| • How many hours does the Earth take to complete one rotation? | 24 hours |
| • How many degrees does the Earth rotate on its axis during one complete rotation? | 360° |
| • How much time does Earth take to complete one rotation in minutes? | 1440 minutes |
| • It takes 1440 minutes to rotate 360°, how much time is required to rotate 1°? | 4 minutes |
| • How much time is required to rotate 15° of angular distance? | 60 minutes (1 hour) |
| • Why is more time recorded in the east and less in the west? | Since the Earth rotates from west to east. |
♦ What is Local time?
The time calculated based on the length of the shadow and position of the Sun is termed as the Local time.
♦ What is the problem faced if there be different local times within a country?
This will create confusion for commonly conducted examinations, railway time, radio telecast etc.
♦ What is Standard Time?
The local time at the Standard Meridian is considered the standard time of the country.
♦ Explain the importance of Standard Time?
The local time at each longitude will be different. If different local times exist within a country, it will create confusion for commonly conducted examinations, railway time, radio telecast, etc. To overcome this crisis, based on an international understanding, countries have selected a longitude, which is a multiple of 7½° longitude as Standard Meridian. The local time at this Standard Meridian is considered as the standard time of the country.
♦ What happens to the size of the circles of latitudes as we move from the equator to the poles?
The size of the circles of latitude decreases from the equator to the poles.
♦ What is the shape of the longitudes?
All longitudes are semicircles.
♦ Importance of Greenwich Mean Time
The longitude that passes through the Royal British Observatory in England is taken as zero-degree meridian. This is called Prime Meridian. The local time at Prime Meridian is called the Greenwich Mean Time. Travellers worldwide calculate time based on Greenwich Time. As the rotation of the Earth is from the west to the east, as we move each longitude east of Greenwich, 4 minutes is added and towards the west 4 minutes is subtracted.
♦ What do travellers worldwide use to calculate time?
Greenwich Mean Time
♦ What is the local time at the Prime Meridian called?
Greenwich Mean Time
♦ How does the time difference change east and west of Greenwich Mean Time?
As the rotation of the Earth is from the west to the east, as we move each longitude east of Greenwich, 4 minutes is added and towards the west 4 minutes is subtracted.
♦ Name the longitude that passes through the Royal British Observatory in England?
Zero-degree meridian (Prime Meridian).
♦ What will be the time at 1° East and 1° West when it is 10:00 A.M. at Greenwich Meridian (0° longitude)?
♦ When it is 9.00 P.M. at Greenwich Meridian (0° longitude), what will the time be at 30° East?
♦ Standard Time of India
The 82 ½° E longitude is considered the standard meridian of India. The local time along this longitude is generally considered as the common time of India. This is known as the Indian Standard Time.
♦ Standard Meridian
Based on an international understanding, countries have selected a longitude, which is a multiple of 7½° longitude as the Standard Meridian.
♦ The Standard Meridian of India
82½° East longitude
♦ What is the time difference between Greenwich Meridian and Indian Standard Meridian (82½° East)?
5.30 hours
♦ What is the time difference between India’s easternmost state, Arunachal Pradesh, and the westernmost state, Gujarat?
About two hours
♦ What are time zones?
Based on international understanding, the world has been divided into 24 zones with 1 hour difference. These are time zones. Each time zone has 15° longitudinal distance
♦ Write examples for countries with large longitudinal extensions have many time zones and Standard Time.
Russia, Canada, the USA, and Australia
♦ Figure 3.23 What is the time and date at 180° East and 180° West when it is December 25 evening 6 p.m. at Greenwich Meridian?
• 180° West - 6 A.M on December 25
♦ Write a short on the International Date Line?
• Based on international agreement, 180° longitude is considered the International Date Line.
• The time difference between east and west sides of 180° longitude is 24 hours.
• Travellers who move westwards crossing the line add a day, and the travellers who move towards the east calculate time by deducting a day.
 Chapter 03 Movements of the Earth: Rotation and Revolution - Questions and Answers | Teachers Handbook){kind=link}
0 Comments