Updated By SaraNextGen

On March 11, 2024, 11:35 AM

Question 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 (as shown in the given figure).

Consider two stars at the end of this bowl. Now, draw an imaginary straight line towards the Northern direction connecting these two stars (as shown in the given figure).

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.

Question 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. With reference to the Earth, the Pole star does not appear to move in the sky because it is located above the axis of rotation of the Earth in the north direction. It appears to remain stationary at a point in the sky.

Question 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:

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 × 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.

Question 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

Volume of a sphere of radius r is given as

Volume of the Earth 

And, volume of Jupiter 

The ratio of the volumes of Jupiter and Earth

Hence, this ratio suggests that Jupiter can accommodate 1331 number of Earths within it.

Question 16:

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

Fig. 17.29

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. The asteroid belt is located between the orbits of Mars and Jupiter. The correct sketch of the solar system is shown in the given figure.