Motions of the Earth - Solutions

 CBSE Class–VI Social Science

NCERT Solutions
Geography Chapter 3
Motions of the Earth

Question 1. Answer the following questions briefly.

  1. What is the angle of inclination of the Earth’s axis with its orbital plane?
    Answer:    The angle of inclination is the angle made by the axis of the earth which is an imaginary line, with its orbital plane. The angle of inclination of the Earth’s axis with its orbital plane is 66.5o.
  2. Define rotation and revolution.
    Answer: Rotation: Rotation is the movement of the earth on its axis. A single rotation of the Earth takes about 24 hours or one day.
    Revolution: The movement of the earth around the sun in a fixed path or orbit is called Revolution. It takes the Earth 365 days to complete it's revolution around the sun.
  3. What is a leap year?
    Answer:
    1. Earth takes 365¼ days to revolve around the Sun. However, for the sake of convenience, we consider a year as consisting of 365 days.
    2. The six hours (¼ th of 24 hours) that are ignored over a span of four years make one day (24 hours).
    3. This surplus day is added to the month of February. Thus, every fourth year, February has 29 days, and such an year (with 366 days) is known as a leap year.
  4. Differentiate between the summer and Winter Solstice.
    Answer:
    Summer SolsticeWinter Solstice
    It is the position of the Earth when the rays of the Sun fall directly on the Tropic of Cancer.It is the position of the Earth when the rays of the Sun fall directly on the Tropic of Capricorn.
    In this position, the North Pole is tilted towards the Sun.In this position, the North Pole is tilted away from the Sun.
    A larger portion of the Northern Hemisphere gets light from the Sun. Hence, it is summer in the Northern Hemisphere.A larger portion of the Southern Hemisphere gets light from the Sun. Hence, it is winter in the Northern Hemisphere.
    During this period, days are longer than nights in the Northern Hemisphere.During this period, nights are longer than days in the Northern Hemisphere.
  5. What is an equinox?
    Answer:    Equinox is the position of the Earth when the rays of the Sun fall directly on the Equator. At this position, neither of the poles is tilted towards the Sun. As a result, the entire Earth has equal days and equal nights.This phenomenon occurs on 21st March and 23rd September.
  6. Why does the Southern Hemisphere experience winter and Summer Solstice in different times than that of the Northern Hemisphere?
    Answer:    When the North Pole is tilted towards the Sun, the Northern Hemisphere experiences Summer Solstice. At this time, as the South Pole is tilted away from the Sun, the Southern Hemisphere experiences Winter Solstice. When the North Pole is tilted away from the Sun, the Northern Hemisphere experiences Winter Solstice. At this time, as the South Pole is tilted towards the Sun, the Southern Hemisphere experiences Summer Solstice.
  7. Why do the Poles experience about six months day and six months night?
    Answer:    The two Poles experience nearly six months of day and six months of night because of the tilt of the Earth on its axis. Because of this tilt, each pole is tilted towards and away from the Sun for about six months each.
    When the North Pole is tilted towards the Sun, it experiences continuous daylight for six months. At the same It is night period at the South Pole. These conditions are reversed when the South Pole is tilted towards the Sun.

Question 2: Tick the correct answers

  1. The movement of the Earth around the Sun is known as
    1. Inclination
    2. Revolution
    3. Rotation
  2. Direct rays of the sun fall on the equator on
    1. 22 June
    2. 21 March
    3. 22 December
  3. Christmas is celebrated in summer in
    1. Japan
    2. India
    3. Australia
  4. Cycle of seasons is caused due to
    1. Revolution
    2. Rotation
    3. Gravitation

Answer:

  1. (ii) Revolution
  2. (ii) 21 March
  3. (iii) Australia
  4. (i) Revolution

Question 3: Fill in the blanks.

  1. A leap year has ________ number of days.
  2. The daily motion of the Earth is _________.
  3. The Earth travels around the Sun in _________ orbit.
  4. The Sun’s rays fall vertically on the Tropic of _________ on 21st June.
  5. Days are shorter during _________ season

Answer:

  1. A leap year has 366 numbers of days.
  2. The daily motion of the Earth is rotational.
  3. The Earth travels around the Sun in a fixed elliptical orbit.
  4. The Sun’s rays fall vertically on the Tropic of Cancer on 21st June.
  5. Days are shorter during winter season.