GEOGRAPHY (VI)- LESSON- 3 MOTIONS OF THE EARTH (QUESTION ANSWERS)

 

GEOGRAPHY (VI)- LESSON- 3

MOTIONS OF THE EARTH

(QUESTION ANSWERS)

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NCERT EXERCISE

1. Answer the following questions briefly.

(a) What is the angle of inclination of the earth’s axis with its orbital plane?

(b) Define rotation and revolution.

(c) What is a leap year?

(d) Differentiate between the Summer and Winter Solstice.

(e) What is an equinox?

(f) Why does the Southern Hemisphere experience Winter and Summer Solstice at different times than that of the Northern Hemisphere?

(g) Why do the poles experience about six months day and six months night?

Answer 1.

(a) The angle of inclination of the earth’s axis with its orbital plane is 66½°.

(b) The movement of the earth on its axis is called rotation. The movement of the earth around the sun in a fixed path or an orbit is called Revolution.

(c) Every fourth year, February has 29 days instead of 28 days. Such a year with 366 days is called a leap year.

(d) Summer Solstice– When the Southern hemisphere experiences the winter season and it is summer in the northern hemisphere. At that point in time, the position of the earth on 21st June is called the Summer Solstice.

Winter Solstice– When the Southern hemisphere experiences the summer season and the reverse occurs at the Northern hemisphere. At that point in time, the position of the earth on 22nd December is called the Winter Solstice.

(e) On 21st March and September 23rd, direct rays of the sun fall on the equator. At this position, neither of the poles is tilted towards the sun. Therefore, the whole earth experiences equal days and equal nights. This is called an equinox.

(f) The Earth is always revolving and it is divided into two hemispheres. The part of the earth which faces the sun experiences summer and the part away from the sun experiences winter. Therefore, Southern Hemisphere experience Winter and Summer Solstice at different times than that of the Northern Hemisphere.

(g) The Poles experience 6 months of day and six months of nights due to the inclination of the earth on its own axis. This inclination keeps one pole towards the sun and another pole away from the sun for 6 months each. This is the reason behind this condition.

2. Tick the correct answers.

(a) The movement of the earth around the sun is known as

(i) Rotation (ii) Revolution (iii) Inclination

(b) Direct rays of the sun fall on the equator on

(i) 21 March (ii) 21 June (iii) 22 December

(c) Christmas is celebrated in summer in

(i) Japan (ii) India (iii) Australia

(d) Cycle of the seasons is caused due to

(i) Rotation (ii) Revolution (iii) Gravitation

Answer 2.

(ii) Revolution

(i) 21 March

(iii) Australia

(ii) Revolution

3. Fill in the blanks.

(a) A leap year has _______________ number of days.

(b) The daily motion of the earth is _______________.

(c) The earth travels around the sun in ______________ orbit.

(d) The sun’s rays fall vertically on the Tropic of ___________ on 21st June.

(e) Days are shorter during ___________ season.

Answer 3.

(a) A leap year has 366 number of days.

(b) The daily motion of the earth is rotation.

(c) The earth travels around the sun in an elliptical orbit.

(d) The sun’s rays fall vertically on the Tropic of Cancer on 21st June.

(e) Days are shorter during winter season.

OTHER IMPORTANT QUESTIONS

Multiple Choice Questions

Choose the correct option to complete the sentences given below:

1. Motion of the earth on its axis in about 24 hours is called
(a) revolution
(b) rotation
(c) both (a) and (b)
(d) none of these

 2. Motion of the earth around the sun is known as
(a) revolution
(b) rotation
(c) both (a) and (b)
(d) none of these

 

 3.What is orbital plane?
(a) Plane formed by the axis
(b) Plane formed by the orbit
(r) Both (a) and (b)
(d) None of these

 

 4. Which one of the following is the source of light on the earth?
(a) The moon
(b) The sun
(c) The satellite
(d) The space

 

 5. The circle that divides the globe into day and night is called
(a) circle of darkness
(b) circle of day and night
(c) circle of illumination
(d)none of these

 

 6. The period of one rotation of the earth is known as
(a) the sun day
(b) the moon day
(c) the earth day
(d) none of these

 

 7. What would have happened if the earth did not rotate?
(a) Cold conditions on earth’s half portion
(b) Warm conditions on earth’s another half portion
(c) No life possible in such extreme conditions
(d) All of these

 

 8. A year with 366 days is called
(a) leap year
(b) normal year
(c) both (a) and (b)
(d) none of these

 

 9. Why do seasons change on the earth?
(a) Due to change in the position of the earth around the sun
(b) Due to no change in the earth’s position
(c) Both (a) and (b)
(d) None of the above

 

 10. When do the longest day and the shortest night occur in the northern hemisphere?
(a) June 21
(b) September 23
(c) December 22
(d) March 21

 

 11. In which season Christmas is celebrated in Australia?
(a ) Winter season
(b) Summer season
(c) Autumn season
(d) Spring season

 

 12. When do equinoxes occur on the earth?
(a) March 21
(b) September 23
(c) Both (a) and (b)
(d) None of these

 

 13. Days and nights occur on earth due to
(a) rotation
(b) revolution
(c) both (a) and (b)
(d) none of these

 

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 14. Change of seasons occurs on earth due to
(a) rotation
(b) revolution
(c) both (a) and (b)
(d) none of these

 

15. The axis of the earth is a/an……………..
(a) imaginary line                              (b) straight line
(c) curved line                                   (d) real line.

16. The earth receives light from the ……………
(a) Moon                                          (b) Stars
(c) Meteors                                        (d) Sun.

17. The time taken by the earth to complete one rotation around its axis is…………………
(a) 24 hours                                        (b) 12 hours
(c) 36 hours                                       (d) 18 hours.

18. The earth completes one revolution in ……………
(a) 366 days                                        (b) 370 days
(c) 365 1/4 days                                (d) 366 1/4 days.

19. It is spring in the Northern Hemisphere and autumn in the Southern Hemisphere on ………………………….
(a) 23rd September                          (b) 21st March
(c) 22nd December                          (d) 21st June.

ANSWERS

1	2	3	4	5	6	7	8	9	10
B	A	A	B	C	C	D	A	A	A
11	12	13	14	15	16	17	18	19	20
A	C	A	B	A	D	A	C	B

 

II. Fill in the Blanks

Fill in the blanks with appropriate words to complete each sentence:

1.   Days and nights occur due to ……………  of the earth.

2.   Only half of the earth gets light from the sun at a time due to its……………. shape.

3.   The period of rotation is known as the ……………..

4.   The sun’s rays fall vertically at the Tropic of…………….. on 22nd December.

5.   On …………  it is autumn season in the Northern Hemisphere and spring in the Southern Hemisphere.

Answer:

1.    rotation

2.    spherical

3.    earth day

4.    Capricorn

5.    23rd September.

III. True/False
Stale whether these sentences are true (T) or false (F).

1.           The axis of the earth makes an angle of 23V& with its orbital plane.

2.           Every five years, February is of 29 days instead of 28 days.

3.           Season changes due to the change in the position of the earth around the   

        sun.

4.           When there is summer in the Northern Hemisphere, it is spring in the

          Southern Hemisphere.

5.           Life is not possible in extreme conditions.

Answer:

1.   False

2.   False

3.   True

4.   False

5.   True.

 

1. Define the circle of illumination.
Answer: The circle that divides the day from night on the globe is known as the circle of illumination.

2. Which motion of the earth is associated with the changes in season?
Answer: Revolution.

3. Why do seasons change? [V. Imp.]
Answer: Seasons change due to the change in the position of the earth around the sun.

4. Why do the areas near the poles receive less heat?
Answer: It is because the rays of the sun are slanting on the poles.

5. When do the longest day and the shortest night occur in the Northern Hemisphere?
Answer: On 21st June.

6. In which Hemisphere does Australia lie?
Answer: Australia lies in the Southern Hemisphere.

7. What would happen if the earth did not rotate? Imp.]
Answer: In such a condition the portion of the earth facing the sun would always experience day, and thus there would be continuous warmth in the region. At the same time, the other half would always remain dark and be freezing cold all the time. These are extreme conditions which are not suitable for life. Thus, we can say that if the earth did not rotate life would not have been possible.

8. How does leap year occur?    
Answer: The earth takes 36514 days Le. one year to complete one revolution around the sun. We consider a year as consisting of 365 days only and ignore six hours for our convenience. Six hours saved every year are added to make one day Le. 24 hours over a span of four years. This surplus day is added to the month of February. Thus every fourth year, February of 29 days instead of 28 days. Such a year with 366 days is called a leap year.