Polestar Lesson 7 Homework

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NCERT Solutions for Class 8th: Ch 17 Stars and the Solar System Science

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NCERT Solutions for Class 8th: Ch 17 Stars and the Solar System Science

Page No: 234

Excercise

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
► (c) A constellation

2. Which of the following is NOT a planet of the sun?
(a) Sirius
(b) Mercury
(c) Saturn
(d) Earth
► (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.
► (a) 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 _________.
(b) The planet which appears reddish in colour is _________.
(c) A group of stars that appear to form a pattern in the sky is known as a __ _________.
(d) A celestial body that revolves around a planet is known as a_________.
(e) Shooting stars are actually not _________.
(f) Asteroids are found between the orbits of __________ and _________.

Answer

(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. ( )
► False

(b) Mercury is the smallest planet of the solar system. ( )
► True

(c) Uranus is the farthest planet in the solar system. ( )
► False

(d) INSAT is an artificial satellite. ( )
► True

(e) There are nine planets in the solar system. ( )
► False

(f) Constellation Orion can be seen only with a telescope. ( )
► False

Page No: 235

6. Match items in column A with one or more items in column B.
(i)Inner planets (a)Saturn
(ii)Outer planets (b)Pole star
(iii)Constellation (c)Great Bear
(iv)Satellite of the Earth(d)Moon
(e)Earth
(f)Orion
(g)Mars

Answer

(i)Inner planets (g), (e)Mars, Earth
(ii)Outer planets (a)Saturn
(iii)Constellation (c), (f)Great Bear, Orion
(iv)Satellite of the Earth(d)Moon

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

Answer

Venus appears in the western sky after sunset and is called the evening star.

8. Name the largest planet of the solar system.
► 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 constellations name are Ursa Major and Orion.

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

Answer

(a) Ursa Major appears like a big dipper. There are three bright stars in the handle and four stars in the bowl of the dipper as shown in below figure.
(b) Orion appears like a hunter. Three bright stars appear in the belt, while five bright stars are arranged in the form of a quadrilateral as shown in the below figure.
11. Name two objects other than planets which are members of the solar system.
Asteroids and Meteors are objects other than planets which are members of the solar system.

Page No: 237

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

Answer

The pole star can be located using the ursa major constellation, by imagining a line towards the Northern direction connecting two stars presnt at the end of the bowl, This imaginary line meets 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.
No, Stars do not move they actually appear to move from east to west due to rotation of earth on its axis from west to east.
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?
The distance of the stars from the Earth and the distance between the stars are very large. It is inconvenient to express these distances in kilometer (km). Thus, these large distances are expressed in light years. One light year is the distance travelled by light in one year. One light year is equal to 9.46 x 1012km.
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 x (9.46 x 1012) = 7.6 x 1013km 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.
Thus, R' = 11 R


















16. Boojho made the following sketch (Fig. 17.29) of the solar system. Is the sketch correct? If not, correct it.
No, the sketch is not correct as the planet 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 which is not correct. The asteroid belt is located between the orbits of Mars and Jupiter. The correct fig is given below.

Versal is a service that allows teachers to build and publish interactive online courses, homework assignments and tutorials. The company launched its service out of beta today, but maybe more importantly, it also announced a partnership with Wolfram Research.

Thanks to this deal with Wolfram Research — which includes Stephen Wolfram joining the Versal board of directors — Versal now allows teachers to embed content from Wolfram into their courses. Currently, this means teachers can use the Wolfram Language to create content. The company tells me that a deeper integration is planned for the future, which will include support for Wolfram Demonstrations, Wolfram|Alpha widgets and other Wolfram resources (if you hadn’t noticed, Stephen Wolfram likes to name products after himself).

“With Versal and our new cloud-based capabilities there’s an amazing opportunity to bring a new level of interactivity and computational knowledge to a very wide range of educational settings,” Wolfram says in a canned statement today. “We’re excited to partner with Versal to make this happen.”

Versal, in many ways, is a reaction to the video-centric learning platforms. Instead, teachers can use the service’s drag-and-drop tool to create new lessons with interactive timelines, quizzes, writing prompts, maps, and diagrams, for example. What’s even more interesting, though, is that developers can write their own widgets, too (in JavaScript). Thanks to this, the service features a music notation widget with a working keyboard, for example. Teachers can write equations with LaTeX, or annotate a 3D skeleton for anatomy lessons.

With today’s release, Versal is bringing the total number of widgets to 48, but the service — surprise, surprise — also offers an online class that teaches you how to build your own gadget.

Teachers who need advanced features like progress tracking, private courses and the ability to invite students have to subscribe to the company’s $5/month Versal Pro plan.

Featured Image: Versal

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