Motions of Earth NCERT Exercise Solution

Question 1: What is the angle of inclination of the earth’s axis with its orbital plane?

Answer: 66.5°

Question 2: Define rotation and revolution.

Answer: Rotation: The movement of earth around its axis is called rotation.
Revolution: The movement of earth on its orbit is called revolution.

Question 3: What is a leap year?

Answer: The year with 366 days is called a leap year.

Question 4: Differentiate between the Summer and Winter Solstice.

Answer: Difference between Summer Solstice and Winter Solstice

• Summer Solstice falls on 21^st June, but Winter Solstice falls on 22^nd December.
• Summer Solstice marks the longest day and shortest night in northern hemisphere, but Winter Solstice marks the longest day and shortest night in southern hemisphere.
• Summer Solstice is during the summer season in northern hemisphere but Winter Solstice is during the summer in southern hemisphere.
• Summer Solstice marks the winter season in southern hemisphere but Winter Solstice marks the winter season in northern hemisphere.

Question 5: What is an equinox?

Answer: The day when day and night are of equal length is called equinox. Equinox falls on 21^st March and 23^rd September.

Question 6: Why does the Southern Hemisphere experience Winter and Summer Solstice in different times than that of the Northern Hemisphere?

Answer: This happens because of the angle between earth’s axis and its orbit. On 21^st June, the sunlight falls directly on the Tropic of Cancer. Hence, it is summer solstice in the northern hemisphere. One 22^nd December, the sunlight falls directly on the Tropic of Capricorn. Hence, it is summer solstice in southern hemisphere.

Question 7: Why do the poles experience about six months day and six months night?

Answer: Because of the angle between the earth’s axis and its orbit, either of the Poles gets sunlight continuously for six months. Due to this, it is six months’ day and six months’ night on the Poles. Between 21^st March and 23^rd September, it is day time on the North Pole and night on the South Pole. Similarly, between 23^rd September and 21^st March; it is day time on the South Pole and night on the North Pole.

Tick the correct answers

The movement of the earth around the sun is known as

1. Rotation
2. Revolution
3. Inclination
   
   Answer: (b) Revolution

Direct rays of the sun fall on the equator on

1. 21 March
2. 21 June
3. 22 December
   Answer: (a) 21 March

Christmas is celebrated in summer in

1. Japan
2. India
3. Australia
   
   Answer: (c) Australia

Cycle of the seasons is caused due to

1. Rotation
2. Revolution
3. Gravitation
   
   Answer: (b) Revolution

Fill in the blanks

1. A leap year has _______________ number of days.
   
   Answer: 366
2. The daily motion of the earth is _______________.
   
   Answer: Earth Day
3. The earth travels around the sun in ______________ orbit.
   
   Answer: Elliptical
4. The sun’s rays fall vertically on the Tropic of ___________ on 21st June.
   
   Answer: Cancer
5. Days are shorter during ___________ season.
   
   Answer: Winter

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