Thursday, 3 March 2016

TEXTBOOK ANSWERS AND SOLUTIONS OF CBSE CLASS VIII SCIENCE Chapter 17 Stars and the Solar System


Exercise

1) Which of the following is NOT a member of the solar system?
(a) An asteroid
(b) A satellite
(c) A constellation
(d) A comet

ANSWER :-(c) Constellation

2) Which of the following is NOT a planet of the sun?
(a) Sirius
(b) Mercury
(c) Saturn
(d) Earth

ANSWER :-(a) Sirius

3) Phases of the moon occur because
(a) We can see only that part of the moon which reflects light towards us.
(b) Our distance from the moon keeps changing.
(c) The shadow of the Earth covers only a part of the moon’s surface.
(d) The thickness of the moon’s atmosphere is not constant.

ANSWER:-(a) Phases of the moon occur because we can see only that part of the moon which reflects light towards us.

4) Fill in the blanks:

(a) The planet which is farthest from the sun is __Neptune__.
(b) The planet which appears reddish in colour is __Mars__.
(c) A group of stars that appear to form a pattern in the sky is known as a __constellation__.
(d) A celestial body that revolves around a planet is known as a satellite_.
(e) Shooting stars are actually not stars __.
(f)Asteroids are found between the orbits of __Mars __ and __Jupiter.

5) Mark the following statement as true (T) or false (F).
(a) Pole star is a member of the solar system. ( )
(b) Mercury is the smallest planet of the solar system. ( )
(c) Uranus is the farthest planet in the solar system. ( )
(d) INSAT is an artificial satellite. ( )
(e) There are nine planets in the solar system. ( )
(f) Constellation Orion can be seen only with a telescope. ( )

ANSWER:-(a) False
(b) True
(c) False
(d) True
(e) False
(f)False

7) In which part of the sky can you find Venus if it is visible as an evening star?

ANSWER:-the western sky

8) Name the largest planet of the solar system.

ANSWER:-The largest planet of the solar system is Jupiter.

9) What is a constellation? Name any two constellations.

ANSWER:-A constellation is a group of stars that form a recognisable pattern in the sky. The two well known constellations are Ursa Major and Orion.

10) Draw sketches to show the relative position of prominent stars in (a) Ursa Major and (b) Orion

ANSWER:-


11) Name two objects other than planets which are members of the solar system.

ANSWER:-(i) Asteroids
(ii) Meteors

12) Explain how you can locate the Pole Star with the help of Ursa Major.

ANSWER:-In order to locate the Pole star in the sky, first of all Ursa Major or Big Dipper constellation must be located. The bowl of the Big Dipper consists of four bright stars. Consider two stars at the end of this bowl. Now, draw an imaginary straight line towards the Northern direction connecting these two stars. This imaginary line meets a star called the Pole Star. The length of the imaginary line from the bowl is about five times the distance between the two stars of the bowl.

13) Do all the stars in the sky move? Explain.

ANSWER:-No. The Earth rotates from West to East on its axis. Hence, all stars in the sky (except the Pole star) appear to move from East to West.

14) Why is the distance between stars expressed in light years? What do you understand by the statement that a star is eight light years away from the Earth?

ANSWER:-One light year is equal to 9.46 × 1012 km. A star is located eight light years away from the Earth. This means that the distance between the star and the Earth is equivalent to the distance travelled by light in eight years, i.e., a star is located 8 × (9.46 × 1012) = 7.6 × 1013 km away from the Earth.

15) The radius of Jupiter is 11 times the radius of the Earth. Calculate the ratio of the volumes of Jupiter and the Earth. How many Earths can Jupiter accommodate?

ANSWER:-Earth and Jupiter can be considered as two spheres with radii R and R’ respectively. Given that the radius of Jupiter is 11 times the radius of the Earth.




16)Boojho made the following sketch (Fig. 17.29) of the solar system. Is the sketch correct? If not, correct it (refer to the book)

ANSWER:-
Planets of the solar system in sequence of their distances from the sun are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Therefore, Boojho’s sketch of the solar system is not correct because he has interchanged the positions of Mars and Venus and also the positions of Uranus and Neptune. Also, he has shown the Asteroid belt in the gap between the orbits of Jupiter and Saturn. This is not correct.


Written By Badal Paul
The author is a passionate blogger, writer and educationalist. This blog is created to ease troubles of the Cbse students. The author holds multiple blogs and the writer of the Novel KALCHAKRA, OOM AND THE CHOSEN FIVE.