STD-5, CHAPTER- 11: OUR SOLAR SYSTEM, EXTRA QUESTION-ANSWERS

 1.      Define solar system.

Ans: The family of sun and its eight planets constitute the solar system.

2.      ______ is the central part of the solar syatem.

Ans: The sun

3.      Why is the sun called a luminous body?

Ans: The sun produces light of its own. So, the sun is said to be a luminous body.

4.      Why the sun appears small to us?

Ans: The sun appears small to us due to its very large distance from the earth.

5.      Name the source of energy for Earth.

Ans: Sun is the source of energy for the Earth.

6.      The sun gives out energy in the form of ______ and _____.

Ans: Heat and light

7.      Define solar energy.

Ans: The energy received from the Sun, is called as solar Energy.

8.      How is the sun useful to us?

Ans: i) The sun is essential for growth, and maintainence, of all forms of life on the earth.

ii)  All living beings, whether plants or animals, depend on the sun for their food.

iii) Plants make their food in the presence of sunlight. All other animals get their food, directly or indirectly, from plants.

9.      Name the devices which use solar energy.

Ans: Solar cookers, Solar geysers and solar cells work through solar energy.

10.  What are the ways in which we use solar energy?

Ans: i) Solar cookers and solar geysers are used for cooking food and getting hot water in our homes.

ii) We also have solar cells that work through solar energy. These are used in devices like the calculators and wrist watches.

iii) Solar cells are also used in man-made satellites and space vehicles.

iv) Solar cells also provide electricity in many remote areas.

11.  Why has the Sun been worshipped as a God?

Ans: The sun is the source of energy for all of us. Being so essential for evolution and propagation of life on earth, it has been worshipped as a God by almost all the ancient civilisations.

12.  What are planets?

Ans: Planets are almost spherical celestial bodies, which move around the sun.

13.  Define revolution.

Ans: When one object moves around another object, it is called as revolution.

14.  Define an Orbit.

Ans: The definite path along which the planets revolve around the sun, is called an orbit.

15.  Name the planets of our solar system in the increasing order of their distances from the sun.

Ans: The planets of the solar system in the increasing order of their distances from the sun, are – Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

16.  Name the closest planet to the sun.

Ans: Mercury is the closest planet to the sun.

17.  Name the smallest planet in our solar system.

Ans: Mercury is the smallest planet in our solar system.

18.  Write four lines about Mercury.

Ans: i) Mercury (Budh) is a dry, hot and almost airless planet.

ii) It is the closest planet to the sun.

iii) There is no atmosphere, around this planet.

iv) The light and heat of the sun, therefore, reach the side of mercury, facing the sun, directly. This side becomes hot and the other side remains comparatively cold.

19.  ‘Venus is the brightest object seen in the sky after the sun and the moon.’- comment.

Ans: Venus reflects back a very large amount of solar energy that falls on it. Venus is, therefore, the brightest object seen in the sky after the sun and the moon.

20.  ‘Venus is hotter than mercury’- Justify.

Ans: Venus has a very thick atmosphere. Its thick atmosphere traps a large amount of solar energy reaching its surface. It is because of this trapping that it is hotter than mercury.

21.  Name the hottest planet of the Solar system.

Ans: Venus

22.  Name the third planet in terms of increasing distance from the sun.

Ans: Earth

23.  Why the surface of earth, appears flat to us?

Ans; The surface of earth, appears to be flat because of its large size.

24.  Why the earth is referred to as the Blue planet?

Ans: The earth reflects sunlight from the water and landmass present on its surface. So, the Earth is referred to as the blue planet.

25.  Define ‘time period of revolution’ or ‘a year’.

Ans: The time taken by a planet to complete one revolution is called its time period of revolution or a year.

26.  How does the time period of revolution change with the distance of planet from the sun/

Ans: The time period of revolution increases as the distance of planet from the sun increases.

27.  Why do the planets not collide among themselves or with the sun?

Ans: Planets do not collide among themselves or with the sun, because the planets are in constant motion around the sun and move in the same direction in orbits that are widely far apart.

28.  What is the time period of revolution for Earth?

Ans: Nearly 365 days.

29.  Different seasons appear on different places on the earth due the _____ of earth around the sun.

Ans: Revolution of Earth.

30.  What is the time period of rotation for earth?

Ans: Nearly 24 hours

31.  ‘Days and nights are due to the rotation of the earth.’- Justify the statement.

Ans: i) During the rotation of Earth, the side facing the sun, receives light and appears bright. This side is said to have day.

ii) The other half then does not receive light from the sun and is said to have night.

iii) The two halves reverse their roles after every half rotation i.e. every 12 hours nearly.

32.  In what ways, the earth is unique?

(OR) State the conditions necessary for existence of life on a planet.

Ans: The conditions necessary for existence of life on a planet are,

i)      Presence of atmosphere

ii)    Presence of (liquid) water on the surface.

iii)  Right size and right distance from the sun

         All these conditions are fulfilled by our earth. It is the only planet that can sustain life on it. This makes earth, a unique planet.

33.  What is the difference between a day and a year?

Ans: i) A day for a planet equals the time taken by it to complete one rotation about its own axis.

ii) A year, on the other hand, equals the time taken by it to complete one revolution around the sun.

34.  Which planet is called as the red planet?

Ans: Mars

35.  Name the planets which have structures similar to that of the earth.

Ans:  Mercury, Venus and Mars have structures similar to that of the earth.

36.  What are terrestrial planets?

Ans: Those planets, which are mostly made up of rocks and metals, are called terrestrial planets.

37.  Name the terrestrial planets.

Ans:  Mercury, Venus, Earth and Mars are the terrestrial planets.

38.  Name the fifth planet of the solar system in terms of the distance from the sun.

Ans: Jupiter is the fifth planet in terms of distance from the sun.

39.  Name the largest planet of the solar system.

Ans: Jupiter

40.  What are planetoids?

Ans: The collection of a large number of very small planets is called as planetoids.

41.  Where does the asteroid belt lie?

Ans: The asteroid belt lies between the orbits of Mars and Jupiter.

42.  Name the second largest planet of the solar system.

Ans: Saturn

43.  Saturn is known as the Ringed planet. Why?

Ans: Saturn has a system of beautiful rings surrounding it. It is therefore, known as the ringed planet.

44.  Name the third largest planet in the solar system.

Ans: Uranus is the third largest planet in the solar system.

45.  Uranus is a _______ without any solid surface.

Ans: Gas giant

46.  Neptune is known as a windy planet. Why?

Ans: Neptune is known as a windy planet, as very strong winds blow on its surface.

47.  Name the Jovian planets. Why are they named so?

Ans: i) Jupiter, Saturn, Uranus and Neptune are the Jovian planets.

ii) Because they are mostly made up of gases and ice.

48.  Name the gaseous planets.

Ans: Jupiter, Saturn, Uranus and Neptune, taken together, are known as gaseous planets.

49.  What is a satellite?

Ans: A satellite is an object that revolves around a much larger object.

50.  Name the two types of satellites?

Ans: The two types of satellites are, i) Natural Satellites and ii) Artificial (man-made) satellites.

51.  What are natural satellites?

Ans: Celestial bodies, which revolve around a planet, are known as the natural satellites of that planet.

52.  Name the natural satellite of the Earth.

Ans: Moon is the natural satellite of the earth.

53.  Name the planets which have a very large number of satellites.

Ans: Saturn and Jupiter

54.  Name the nearest neighbour of earth in space.

Ans: Moon

55.  Why is the moon called a non-luminous object?

Ans: Moon does not have its own light. It only reflects a part of sunlight falling on it. So, it is a non-luminous object.

56.  What is the time period of revolution of moon around the earth?

Ans: Nearly 28 days

57.  Why do we observe phases of moon?

Ans: Because of the changes in the relative position of the earth and the moon, with respect to the sun, we observe the gradual change of shape and size of the moon everyday, which we call as the phases of the moon.

58.  Name the different phases of the moon.

Ans: The phases of the moon include, i) Completely dark phase-amavas or new moon day

ii) a complete bright phase- poornima or full moon day

59.  What is the time gap between amavas and poornima?

Ans: Nearly 15 days

60.  Write the meaning of the term ‘Artificial satellites’.

Ans: Artificial satellites are man-made objects, which can be made to revolve around the earth.

61.  State the uses of artificial satellites.

Ans: i) Artificial satellites are used in communication for transmitting radio, telephone and television signals.

ii) They are also used for weather forecasting and remote sensing.

iii) Artificial satellites are also being used to collect information about the other planets and the stars.

62.  Name the first satellite launched by India.

Ans: Aryabhatta (in 1975)

63.  Name some artificial satellites launched by India.

Ans: Rohini, Apple, INSAT, EDUSAT, CARTOSAT, IMS-1, Chandrayan-1, GSAT-4, Jugnu and SARAL are some satellites launched by India.

64.  In which year, India launched chandrayan-1?

Ans: October 2008 (by ISRO)

65.  What are geo-stationary satellites?

Ans: Those satellites which take as much time to complete one orbit around the earth as the time taken by the earth to complete one rotation on its axis, are called as geo-stationary satellites.