1. What are celestial bodies?
Ans. The stars, the planets, the moon and many other objects in the sky are called celestial objects.
2. What is a natural satellite?
4. Which comet appears after every 76 years?
Ans. Halley’s comet appears after nearly every 76 years. It was last seen in 1986.
5. Name any two artificial satellites of our country.
Ans. Aryabhatta and INSAT are two artificial satellites of our country.
6. Name a star that always appear stationary from Earth's surface?
Ans. Pole star always appear stationary from earth's surface.
7. Why do we classify the Sun as a star?
Ans. Stars are celestial bodies that emit light of their own. and Sun is naturally luminous body, so Sun is a Star.
8. Why does the moon change its shape every day?
Ans. The moon does not produce its own light. We see the moon because the sunlight falling on it gets reflected towards us. We therefore, see only that part of the moon, from which the light of the Sun is reflected towards us.The size of the illuminated part of the moon visible from the Earth increases each day after the new moon day. After the full moon day, the sunlit part of the moon visible from the Earth decreases in size every day. It is due to relative position of earth, moon and sun.
9.Why the village sky is so different from the night sky in big cities?
Ans. Due to pollution the night sky in big cities different from the village sky.
10.The Sun rises in the east and sets in the west. Why?
Ans. Sun appears to rise in the east and set in the west as the Earth rotates from west to east on its axis.
11. What do you understand by light year? What is its value in km?
Ans. Light year is the distance travelled by light in one year.It is used to measure the large distance between stars and planets.
12. What is a Pole star?
Ans. The pole star is situated in the direction of the earth’s axis. It does not appear to move. The Pole star lies close to the axis of rotation of the Earth.
13. Give reason for
(i) Change in seasons on the earth
(ii) Different phases of moon.
Ans. (i) The reason for changing in season on the earth is the revolution of earth around the Sun.
(ii) Different phases of moon is due to relative position of earth, moon and sun.
15. Why meteors are called shooting stars even though they are not stars?
Ans. A meteor is usually a small object that occasionally enters the earth’s atmosphere. At that time it has a very high speed. The friction due to the atmosphere heats it up. It glows and evaporates . A bright steak appears for a very short time and it is called shooting star.
16. Which constellation is called 'Hunter'?
Ans. Orion is called the Hunter. It can be seen during winter in the late evenings.It has seven or eight bright stars.The three middle stars represent the belt of the hunter.The four bright stars appear to be arranged in the form of a quadrilateral.
17. What is constellation? Name any three constellations?
Ans. The stars forming a group that has a recognisable shape is called a constellation.
Three constellations are Ursa major Ursa minor, Cassiopeia and Orion.
18. Can we hear any sound on the Moon?
Ans. Sound cannot travel when there is no medium. So we can not hear any sound on the moon.
19. What are galaxies?
Ans. Galaxies are the huge collection of stars gas and dust.
20. Write the uses of artificial satellites.
Ans. Uses of artificial satellite:
(i) For weather forecasting
(ii) Communication
(iii) Global positioning system.
(iv) Scientific investigation.
21. Write short notes on Meteors and Meteorites.
Ans. A meteor is usually a small object of outer space that occasionally enters the earth’s atmosphere. At that time it has a very high speed. The friction due to the atmosphere heats it up. It glows and evaporates quickly and due to this we can see brite streak.These Streak of a Meteor are commonly known as shooting stars.
Some meteors are large so that they can reach the Earth before they evaporate completely. The body that reaches the Earth is called a meteorite. Meteorites help scientists in investigating the nature of the material from which the solar system was formed.
22. What is the difference between a star and a constellation?
Ans. Stars are celestial bodies that emit light of their own and the stars forming a group that has a recognisable shape is called a constellation.
23. Give one word for each
Ans. The stars, the planets, the moon and many other objects in the sky are called celestial objects.
2. What is a natural satellite?
Ans. The natural satellite is a celestial body revolving around another celestial body. The moon is a natural satellite of the earth. The earth is a natural satellite of the Sun.
3. Write the name of first satellite of India.
Ans. ISRO built first satellite Aryabhata.
4. Which comet appears after every 76 years?
Ans. Halley’s comet appears after nearly every 76 years. It was last seen in 1986.
Ans. Aryabhatta and INSAT are two artificial satellites of our country.
6. Name a star that always appear stationary from Earth's surface?
Ans. Pole star always appear stationary from earth's surface.
7. Why do we classify the Sun as a star?
Ans. Stars are celestial bodies that emit light of their own. and Sun is naturally luminous body, so Sun is a Star.
Ans. The moon does not produce its own light. We see the moon because the sunlight falling on it gets reflected towards us. We therefore, see only that part of the moon, from which the light of the Sun is reflected towards us.The size of the illuminated part of the moon visible from the Earth increases each day after the new moon day. After the full moon day, the sunlit part of the moon visible from the Earth decreases in size every day. It is due to relative position of earth, moon and sun.
9.Why the village sky is so different from the night sky in big cities?
Ans. Due to pollution the night sky in big cities different from the village sky.
10.The Sun rises in the east and sets in the west. Why?
Ans. Sun appears to rise in the east and set in the west as the Earth rotates from west to east on its axis.
11. What do you understand by light year? What is its value in km?
Ans. Light year is the distance travelled by light in one year.It is used to measure the large distance between stars and planets.
12. What is a Pole star?
Ans. The pole star is situated in the direction of the earth’s axis. It does not appear to move. The Pole star lies close to the axis of rotation of the Earth.
13. Give reason for
(i) Change in seasons on the earth
(ii) Different phases of moon.
Ans. (i) The reason for changing in season on the earth is the revolution of earth around the Sun.
(ii) Different phases of moon is due to relative position of earth, moon and sun.
15. Why meteors are called shooting stars even though they are not stars?
Ans. A meteor is usually a small object that occasionally enters the earth’s atmosphere. At that time it has a very high speed. The friction due to the atmosphere heats it up. It glows and evaporates . A bright steak appears for a very short time and it is called shooting star.
16. Which constellation is called 'Hunter'?
Ans. Orion is called the Hunter. It can be seen during winter in the late evenings.It has seven or eight bright stars.The three middle stars represent the belt of the hunter.The four bright stars appear to be arranged in the form of a quadrilateral.
17. What is constellation? Name any three constellations?
Ans. The stars forming a group that has a recognisable shape is called a constellation.
Three constellations are Ursa major Ursa minor, Cassiopeia and Orion.
18. Can we hear any sound on the Moon?
Ans. Sound cannot travel when there is no medium. So we can not hear any sound on the moon.
19. What are galaxies?
Ans. Galaxies are the huge collection of stars gas and dust.
20. Write the uses of artificial satellites.
Ans. Uses of artificial satellite:
(i) For weather forecasting
(ii) Communication
(iii) Global positioning system.
(iv) Scientific investigation.
21. Write short notes on Meteors and Meteorites.
Ans. A meteor is usually a small object of outer space that occasionally enters the earth’s atmosphere. At that time it has a very high speed. The friction due to the atmosphere heats it up. It glows and evaporates quickly and due to this we can see brite streak.These Streak of a Meteor are commonly known as shooting stars.
Some meteors are large so that they can reach the Earth before they evaporate completely. The body that reaches the Earth is called a meteorite. Meteorites help scientists in investigating the nature of the material from which the solar system was formed.
22. What is the difference between a star and a constellation?
Ans. Stars are celestial bodies that emit light of their own and the stars forming a group that has a recognisable shape is called a constellation.
(a) Stars forming a recognizable pattern.
(b) A solid body from outer space that is sometimes able to reach the earth‟s surface.
(c) A belt of small planetoids present mainly in between the orbits of Mars and Jupiter.
Ans. (a) Constellation.
(b) Meteorite.
(c) Asteroids.
24. What are asteroid?
Ans. There is a large gap in between the orbits of Mars and Jupiter. This gap is occupied by a large number of small objects that revolve around the Sun. These are called asteroids.
25. Give some details about Moon.
Ans. Moon is a natural satellite which revolves around the earth. It does not emit its won light. It reflects light of sun.It has no atmosphere. It has no water. Life cannot exist on the moon.
Ans. (a) Constellation.
(b) Meteorite.
(c) Asteroids.
24. What are asteroid?
Ans. There is a large gap in between the orbits of Mars and Jupiter. This gap is occupied by a large number of small objects that revolve around the Sun. These are called asteroids.
25. Give some details about Moon.
Ans. Moon is a natural satellite which revolves around the earth. It does not emit its won light. It reflects light of sun.It has no atmosphere. It has no water. Life cannot exist on the moon.
26. What do you mean by solar system?Give names of the planets in our solar system in increasing order of distance from the sun?
Ans. The Sun and the celestial bodies which revolve around it form the solar system. It consists of large number of bodies such as planets, comets, asteroids and meteors. The gravitational attraction between the Sun and these objects keeps them revolving around it.
Names of the planets in our solar system in increasing order of distance from the sun :
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune.
Ans. (a) The largest planet- Jupiter.
28. The planets do not collide while revolving around the Sun. Explain?
Ans. The planets do not collide while revolving around the Sun because all planets are revolved around the sun in a fixed orbit and orbits do not cross each other.
29. What do you mean by the term moon phase. Explain various phases of the moon?
Ans. The various shapes of the bright part of the moon as seen during a month are called the moon phase.
The day on which the whole disc of the moon is visible is known as the full moon day. Thereafter, every night the size of the bright part of the moon appears to become thinner and thinner. On the fifteenth day the moon is not visible. This day is known as the new moon day. The next day, only a small portion of the moon appears in the sky. This is known as the crescent moon. Then again the moon grows larger every day. On the fifteenth day once again we get a full view of the moon.
30. Explain the constellation Orion?
Ans. Orion is another well-known constellation that can be seen during winter in the late evenings. It is one of the most magnificent constellations in the sky. It also has seven or eight bright stars. Orion is also called the Hunter. The three middle stars represent the belt of the hunter. The four bright stars appear to be arranged in the form of a quadrilateral.
31. What do you understand by the terms, period of rotation and period of revolution of a planet?
Ans. The time taken by a planet to complete one revolution is called its period of revolution whereas, the time taken by a planet to complete one rotation is called its period of rotation.
32. If we imagine Saturn in a large pool of water then it will float. Why?What makes it unique in the solar system ?
Ans. Yes, it will float because the density of saturn is less than water.
In the solar system its beautiful rings makes it unique.
33. What is a meteor shower?
Ans.When the Earth crosses the tail of a comet, swarms of meteors are seen. These are known as meteor showers. Some meteor showers occur at regular intervals each year.
34. What are comets?
Ans. Comets are also members of our solar system. They revolve around the Sun in highly elliptical orbits. Their period of revolution round the Sun is usually very long. A Comet appears generally as a bright head with a long tail. The length of the tail grows in size as it approaches the sun. The tail of a comet is always directed away from the sun. comets are known to appear periodically. One such comet is Halley’s comet, which appears after nearly every 76 years.
35. Differentiate with examples artificial and natural satellites?
Ans. i. The artificial satellites are man-made, they are launched from the Earth, Natural satellite are formed by nature.
ii. Artificial satellite revolves around the Earth much closer than earth’s natural satellite, the moon.
iii. Artificial satellite are used for forecasting weather, transmitting television and radio signals. They are also used for telecommunication and remote sensing, Whereas natural satellites are not.
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Names of the planets in our solar system in increasing order of distance from the sun :
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune.
27. In the solar system, name the following:
(a) The largest planet,
(b) The smallest planet,
(c) The brightest planet ,
(d) The planet with largest number of satellites.Ans. (a) The largest planet- Jupiter.
(b) The smallest planet - Mercury.
(c) The brightest planet - Venus.
(d) The planet with largest number of satellites - Saturn.28. The planets do not collide while revolving around the Sun. Explain?
Ans. The planets do not collide while revolving around the Sun because all planets are revolved around the sun in a fixed orbit and orbits do not cross each other.
29. What do you mean by the term moon phase. Explain various phases of the moon?
Ans. The various shapes of the bright part of the moon as seen during a month are called the moon phase.
The day on which the whole disc of the moon is visible is known as the full moon day. Thereafter, every night the size of the bright part of the moon appears to become thinner and thinner. On the fifteenth day the moon is not visible. This day is known as the new moon day. The next day, only a small portion of the moon appears in the sky. This is known as the crescent moon. Then again the moon grows larger every day. On the fifteenth day once again we get a full view of the moon.
30. Explain the constellation Orion?
Ans. Orion is another well-known constellation that can be seen during winter in the late evenings. It is one of the most magnificent constellations in the sky. It also has seven or eight bright stars. Orion is also called the Hunter. The three middle stars represent the belt of the hunter. The four bright stars appear to be arranged in the form of a quadrilateral.
31. What do you understand by the terms, period of rotation and period of revolution of a planet?
Ans. The time taken by a planet to complete one revolution is called its period of revolution whereas, the time taken by a planet to complete one rotation is called its period of rotation.
32. If we imagine Saturn in a large pool of water then it will float. Why?What makes it unique in the solar system ?
Ans. Yes, it will float because the density of saturn is less than water.
In the solar system its beautiful rings makes it unique.
33. What is a meteor shower?
Ans.When the Earth crosses the tail of a comet, swarms of meteors are seen. These are known as meteor showers. Some meteor showers occur at regular intervals each year.
34. What are comets?
Ans. Comets are also members of our solar system. They revolve around the Sun in highly elliptical orbits. Their period of revolution round the Sun is usually very long. A Comet appears generally as a bright head with a long tail. The length of the tail grows in size as it approaches the sun. The tail of a comet is always directed away from the sun. comets are known to appear periodically. One such comet is Halley’s comet, which appears after nearly every 76 years.
35. Differentiate with examples artificial and natural satellites?
Ans. i. The artificial satellites are man-made, they are launched from the Earth, Natural satellite are formed by nature.
ii. Artificial satellite revolves around the Earth much closer than earth’s natural satellite, the moon.
iii. Artificial satellite are used for forecasting weather, transmitting television and radio signals. They are also used for telecommunication and remote sensing, Whereas natural satellites are not.
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