## NCERT Solutions for Class 6th Social Science Geography Chapter 3 Motions of the Earth

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 solstice and winter solstice.
(e) What is an equinox?
(f) Why does the Southern Hemisphere experience winter and summer solstice in different times than that of the Northern Hemisphere?
(g) Why do the poles experience about six months day and six months night?
Answer: (a) The angle of inclination of the earth’s axis with its orbital plane is 66’/a.
(b) The movement of the earth on its axis is known as rotation.
Revolution. The movement of the earth around the sun in a fixed path or orbit is known as revolution.
(c) The year in which Februaiy is of 29 days instead of 28 days is called a leap year. Thus a leap year is of 366 days instead of 365 days.
(d) Difference between summer solstice and 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 entire earth experiences equal days and equal nights. This phenomenon is called an equinox.
(f) Since it is winter in the Southern Hemisphere when it is summer in the Northern Hemisphere, therefore the position of the earth ‘which is called the Winter Solstice in one Hemisphere is the Summer Solstice in the other, and vice-versa.
(g) The axis of the earth is tilted, due to which the sun continuously either shines or cannot be seen for a long time here. Although the earth rotates and day changes into night and night into day at other places, but the poles remain under the same stage for a much longer time due to the tilt.
(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
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…………….
(d)The sun’s rays fall vertically on the Tropice of…………….. on 21st June.
(e)Days are shorter during …………
Answer: (a)366, (b) rotation, (c) elliptical, (d) cancer, (e) winter.
I.Multiple Choice Questions
Choose the correct option to complete the sentences given below:
(i) The axis of the earth is a/an……………..
(a) imaginary line                              (b) straight line
(c) curved line                                   (d) real line.
(ii) The earth receives light from the ……………
(a) Moon                                          (b) Stars
(c) Meteors                                        (d) Sun.
(iii) 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.
(iv) The earth completes one revolution in ……………
(a) 366 days                                        (b) 370 days
(c) 365 1/4 days                                (d) 366 1/4 days.
(v) 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.
Answer: (i)—(a), (ii)—(d), (iii)—(a), (iv)—(c), (v)—(b).
II.Fill in the Blanks
Fill in the blanks with appropriate words to complete each sentence:                         .
(i) Days and nights occur due to ……………  of the earth.
(ii) Only half of the earth gets light from the sun at a time due to its……………. shape.
(iii)The period of rotation is known as the ……………..
(iv) The sun’s rays fall vertically at the Tropic of…………….. on 22nd December.
(v) On …………  it is autumn season in the Northern Hemisphere and spring in the Southern Hemisphere.
(iii) earth day         (iv) Capricorn           (v) 23rd September.
III. True/False
Stale whether these sentences are true (T) or false (F).
(i) The axis of the earth makes an angle of 23V& with its orbital plane.
(ii) Every five year, February is of 29 days instead of 28 days.
(iii) Season changes due to the change in the position of the earth around the sun.
(iv)  When there is summer in the Northern Hemisphere, it is spring in the Southern Hemisphere.
(v) Life is not possible in extreme conditions.
Answer: (i) False, (ii) False, (iii) True, (iv) False, (v) True.
IV. Matching Skill
Match the items in column A correctly with those given in column B.
V. Very Short Answer Type Questions
1. Define circle of illumination.
Answer: The circle that divides the day from night on the globe is known as circle of illumination.
2. Which motion of earth is associated with the changes in season?
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?