Motions of Earth

NCERT Solution

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

Answer: 66.5°

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.

What is a leap year?

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


Differentiate between the Summer and Winter Solstice.

Answer:

Summer SolsticeWinter Solstice
Falls on 21st June.Falls on 22nd December.
Longest day and shortest night in northern hemisphere.Longest day and shortest night in southern hemisphere.
Summer season in northern hemisphere.Summer in southern hemisphere.
Winter in southern hemisphere.Winter in northern hemisphere.

What is an equinox?

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

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 21st June, the sunlight falls directly on the Tropic of Cancer. Hence, it is summer solstice in the northern hemisphere. One 22nd December, the sunlight falls directly on the Tropic of Capricorn. Hence, it is summer solstice in southern hemisphere.

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 21st March and 23rd September, it is day time on the North Pole and night on the South Pole. Similarly, between 23rd September and 21st 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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