# Samacheer Kalvi 9th Science Solutions Chapter 9 Pdf

## Samacheer Kalvi 9th Science Solutions Chapter 9 Pdf

Tamilnadu Board Samacheer Kalvi 9th Science Solutions Chapter 9: Tamilnadu State Board Solution Class 9 Science Chapter 9 – UNIVERSE.

### Samacheer Kalvi 9th Science Solutions Chapter 9: Overview

 Board Samacheer Kalvi Class 9 Subject Science Chapter 9 Chapter Name UNIVERSE

### Samacheer Kalvi 9th Science Solutions Chapter 9 Pdf

Chapter 9

UNIVERSE

Exercise:

1)  Who proposed the heliocentric model of the universe?

(a) Tycho Brahe

(b) Nicolaus Copernicus

(c) Ptolemy

(d) Archimedes

Ans:  (b) Nicolaus Copernicus

Because, Nicolaus Copernicusproposed the heliocentric model of the universe.

2) Which of the following is not a part of outer solar system?

(a) Mercury

(b) Saturn

(c) Uranus

(d) Neptune

Ans: (a) Mercury

Because, four large planets Jupiter, Saturn, Uranus and Neptune spread out in the outer solar system and slowly orbits around the sun are called as outer planets.

3) Ceres is a _______.

(a) Meteor

(b) Star

(c) Planet

(d) Asteroid

Ans: (d) Asteroid

Because, Ceres is the biggest asteroid.

4) The period of revolution of planet A around the Sun is 8 times that of planet B. How many times is the distance of planet A as great as that of planet B?

(a) 4

(b) 5

(c) 2

(d) 3

Ans: (a) 4

According to Kepler’s third law of planetary motion, the square of time of period of revolution of a planet around the sun is directly proportional to the cube of the distance between the sun and the planet.

Here, TA = 8 TB

And, (TA/TB)2 = (RA/RB)3

(TA/TB)2/3 =  (RA/RB)             since, taking power 1/3 on both sides.

(8TB/TB)2/3=  (RA/RB)             since, TA = 8 TB

(23)2/3= (RA/RB)

4 = (RA/RB)

RA = 4RB

5) The Big Bang occurred _____ years ago.

(a) 13.7 billion

(b) 15 million

(c) 15 billion

(d) 20 million

Ans: (a) 13.7 billion

Because, The Big Bang occurred 13.7 billion years ago.

Fill in the blanks.

1) The speed of Sun in km/s is _______.

Ans:The speed of Sun in km/s is 200 km/s.

2) The rotational period of the Sun near its poles is ________.

Ans:The rotational period of the Sun near its poles is35 days.

3) India’s first satellite is _______.

Ans:India’s first satellite isAryabhata.

It was launched on 19th April 1975.

4) The third law of Kepler is also known as the Law of ________.

Ans:The third law of Kepler is also known as the Law ofHarmonics.

5) The number of planets in our Solar System is _______.

Ans:The number of planets in our Solar System iseight.

The planets from near to sun are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

III. State whether true or false. If false, correct the statement.

1) ISS is a proof for international cooperation.

Ans:  True

The ISS i.e. International Space Station is the large spacecraft in the orbit around the earth and which represents most important model for international cooperation.

2) Halley’s comet appears after nearly 67 hours.

Ans: False

Because, Halley’s comet appears after nearly 76 years.

3) Satellites nearer to the Earth should have lesser orbital velocity.

Ans: False

Since, satellites nearer to the Earth should have higher orbital velocity.

4) Mars is called the red planet.

Ans: True

Mars is called as red planet because the iron minerals in soil get oxidize or rust which causes the atmosphere and soil to look red.

1) What is solar system?

Ans:

The sun and the celestial bodies which are revolving around the sun forms the solar system. Solar system consist of large no. of bodies like planets, comets, asteroids and meteors. This bodies are revolving around the sun in particular orbits because of the gravitational force of attraction between the sun and them.

2) Define orbital velocity.

Ans: The satellites are revolving around the planet in particular orbit due to the gravitational force between the planet and satellites. The satellites are carried by rocket to a particular height and then they are released with particular high velocity so that they can revolve in a particular circular orbit. The horizontal velocity given to the satellite at a particular height so that it revolves in a fixed circular orbit around the planet is called as orbital velocity. The orbital velocity depends on the height of the satellite above the earth. For nearer objects to the earth the velocity required must be faster than velocity for the objects which are at a high altitude from the earth’s surface

3) Define time period of a satellite.

Ans:  The time taken by the satellite to complete one revolution around the earth is called as the time period of that satellite. Hence, time period is given by,

Time period T = distance covered / orbital velocity

T = 2πr/ v

T = 2π (R+h)/ √ (GM/R+h)

Where v is the orbital velocity of the satellite at a height h from the earth’s surface.

4) What is a satellite? What are the two types of satellites?

Ans: The body moving in a particular fixed orbit around the planet is called as satellite. There are two types of satellites artificial or manmade satellites and natural satellites. For example: earth and moon are the natural satellites. The earth revolves around the sun and moon revolves around the earth. Artificial satellites are the machines which are launched in space and revolves around particular object in the space.

5) Write a note on the inner planets.

Ans: In our solar system there are inner and outer planets which are defined on the basis of their distance from the sun. All this planets are separated unevenly. The first four planets are closed to each other and closed to the sun also. This planets forms the inner solar system and they are called as inner planets. The four inner planets are Mercury, Venus, Earth and Mars. This planets are called as rocky planets due to the presence of solid rock crust on their surface. Their insides, surfaces and atmosphere are in similar pattern. That’s why our earth is taken as the model of the other three planets also.

Ans: Comets are the lumps of the dust and ice which are revolving around the sun in a highly elliptical orbits, due to which their period of revolution is very long. When this comets reaches to the sun vaporizes and converted into head and tail. Some comets are seen periodically, like Halley’s Comet which appears after nearly every 76 years. Lastly it was seen in 1986 and it will see in future in 2062.

7) State Kepler’s laws.

Ans: Johannes Kepler was proposed the three laws of planetary motion which are as follows.

First law: According to this law, all planets are revolving around the sun in an elliptical orbits with sun being one of their foci.

This law is also called as Law of ellipses.

Second law: According to this law, the line connecting the sun and planet covers equal area in equal interval of time.

This law is also called as Law of equal areas.

Third law: According to this law, the square of time period of revolution of a planet around the sun is directly proportional to the cube of the distance between the sun and the planets.

This law is also called as law of Harmonics.

8) What factors have made life on Earth possible?

Ans:

There are lots of reason or factors due which life on the earth is possible while on the other planets it is not.

The atmosphere and the gases in the atmosphere are responsible for the growth and development of human and wild life on the earth.

Externally, earth is also surrounded by layers of atmosphere and ozone layer also, due to which ultraviolet rays from sun are opposed on reaching the earth.

Also, the earth is not nearest and not far from sun due to which it is not too hot and not too cool as compared to other planets.

The environment on the earth is responsible for the living things. The plants produces food by taking CO2 form the atmosphere and releases oxygen, which is the main source for human being to live.

The one fourth part of earth is surrounded by water which is taking part in maintaining the environmental cycle stable.

Overall, the things which are required to live the life are present only on the earth and are suitable also, so the life on the earth is possible.

Scientist are trying to make life possible on the moon and mars also for future purpose.

1) Give an account of all the planets in the solar system.

Ans:

All the planets are revolving around the sun in a particular elliptical orbit. Time required to complete one revolution is called as period of revolution. Along with revolving around the sun each planet rotates about its own axis of rotation like a top. The time required to complete one rotation is called as period of rotation. The period of rotation of earth is 23 hours 56 minutes and on earth it is considered as 24 hours.

This all planets are unevenly spaced. First four planets are very close to each other and also to the sun, so this four planets forms the inner solar system and they are called as inner planets. The inner planets are Mercury, Venus, Earth and Mars. The remaining four planets which are spread outerly and revolving slowly around the sun are Jupiter, Saturn, Uranus and Neptune. And this planets forms the outer solar system and they are called as outer planets.

1) Mercury: Mercury is the nearest planet to the sun which is rocky and very hot during day but too cold at night. The Mercury planet can be seen through telescope easily from earth which looks very small and faint.

2) Venus: Venus is the special planet having size same as the earth and it is hottest planet in the solar system. Venus spins in opposite direction to the all other planets. Hence, on Venus sun rises in West and sets in east.

3) Earth: the earth is only one planet in the solar system which has living life. Because of its right distance from the sun, presence of water, suitable atmosphere for living organisms and a protective ozone layer around it which protect us from UV rays. From space our earth looks bluish green due the reflection of light from water and land mass.

4) Mars: Mars is the first planet outside the earth’s orbit. It looks reddish so it is also called as red planet. It has two natural satellites Deimos and Phobos.

5) Jupiter: Jupiter is also called as Giant planet. It is largest planet in our solar system. It has 3 rings and 65 moons. Its moon Ganymede is the largest moon of our solar system.

6) Saturn: Saturn looks yellowish in colour and it is the second largest and a giant gas planet in our solar system. It is well known for its bright shiny rings. It has overall 60 moons and largest one is the Titan.

7) Uranus: Uranus is one of the cold gas giant planet in our solar system and can be visible only through the large telescope. Due to the presence of peculiar tilt it has longest summers and winters and each lasting for 42 years.

8) Neptune: Neptune is 8th planet of our solar system and it is greenish in colour. After every 248 years Pluto crosses its orbit. It has 13 moons out of which Triton is the largest one. And it is the only one planet in our solar system which is rotating in the opposite direction to the spinning of planet.

2) Discuss the benefits of ISS.

Ans:

ISS i.e. International Space Station is the large spacecraft which can house the astronauts and science laboratory. It is the largest manmade object in space which is also seen from the earth surface through our naked eye. According to NASA, following are the ways through which ISS is beneficing us.

Supporting water purification efforts: With the technology developed for ISS, areas having water scarcity can be gained to access the advanced water filtration and purification systems. The WRS and OGS are the systems developed for the ISS has already saved a village in Iraq from being deserted due to the lack of clean water.

Eye tracking technology: The eye tracking technology is developed for a microgravity experiments. In many laser surgeries it has been proved as an ideal. This technology is helping disabled people having limited movement and speech.

Robotic arms and surgeries: Robotic technology is helping to the surgeons in removing inoperable tumors. Also, the inventors told that the robot could take the biopsies with remarkable precision and consistency. There are many researches taking place in the ISS are useful like development of improved vaccines, breast cancer detection and treatment, ultrasound machines for remote places.

3) Write a note on orbital velocity.

Ans:  The satellites are revolving around the planet in particular orbit due to the gravitational force between the planet and satellites. The satellites are carried by rocket to a particular height and then they are released with particular high velocity so that they can revolve in a particular circular orbit. The horizontal velocity given to the satellite at a particular height so that it revolves in a fixed circular orbit around the planet is called as orbital velocity. The orbital velocity depends on the height of the satellite above the earth. For nearer objects to the earth the velocity required must be faster than velocity for the objects which are at a high altitude from the earth’s surface

Conceptual questions.

1) Why do some stars appear blue and some red?

Ans: The fundamental building blocks of the galaxies are the stars. Stars are formed in Big Bang when galaxies are formed. Stars are producing radiations like heat, light, UV rays, x-rays and other also. The stars are mainly composed of gas and plasma. Stars are built from hydrogen gases, hydrogen atoms get fused to form helium atoms and large amount of heat is released in this process. The brightness of stars depends on their intensity and also on the distance from the earth. The stars are of different colours depending on their temperature. The stars having more temperature i.e. stars which are too hot are white or blue in colour. And the stars which are having low temperature i.e. cool are orange or red in colour.

2) How is a satellite maintained in nearly circular orbit?

Ans:  A body moving in an orbit around the sun is called as satellite. There are two types of satellite manmade or artificial satellites and natural satellites. Moon is the satellite of earth and we can see it because it reflects the light of sun. This satellites are moving around the planets due to the gravitational and centripetal force. Except mercury and Venus all the planets have their moons. Many artificial satellites are launched by man in space. The first satellite launched is Sputnik in 1956 and the India’s first satellite launched is Aryabhatta on 19th April 1975. The satellites are moving in a particular orbits above a specific height in km. This satellites are carried by rockets and released horizontally at particular height such that it rotates in a circular orbit. At  particular height the friction due to air is negligible due to which it can give a particular velocity to rotate in a circular orbit. The particular height given to a satellite at particular height in order to rotate in a circular orbit is called as orbital velocity of satellite. This orbital velocity depends on the height of the planet above the earth. Nearer the satellite to the planet the orbital velocity required must be faster.

3) Why some satellites are called geostationary?

Ans: A body moving in an orbit around the sun is called as satellite. There are two types of satellite manmade or artificial satellites and natural satellites. Moon is the satellite of earth and we can see it because it reflects the light of sun. This satellites are moving around the planets due to the gravitational and centripetal force. Except mercury and Venus all the planets have their moons. Many artificial satellites are launched by man in space. The first satellite launched is Sputnik in 1956 and the India’s first satellite launched is Aryabhatta on 19th April 1975. The satellites are moving in a particular orbits above a specific height in km. This satellites are carried by rockets and released horizontally at particular height such that it rotates in a circular orbit. At a particular height the friction due to air is negligible due to which it can give a particular velocity to rotate in a circular orbit. The particular height given to a satellite at particular height in order to rotate in a circular orbit is called as orbital velocity of satellite. This orbital velocity depends on the height of the planet above the earth. Nearer the satellite to the planet the orbital velocity required must be faster. For 200 km of height the orbital velocity required is nearly 27400 kph. The orbital velocity and the distance permits to complete one revolution in 24 hrs. Earth is completing one rotation in 2r hrs. And a satellite stays in a fixed position relative to the point on the earth’s surface. Because, the satellite stays all the time on a same spot and this orbit is called as geostationary orbit. And hence such satellites are also called as geostationary satellites.

4) A man weighing 60 kg in the Earth will weigh 1680 kg in the Sun. Why?

Ans:  The weight of the man is different on the sun and on the earth, because of the different acceleration due to gravity. The acceleration due to gravity on earth is 9.8 m/s2 and on the sun it is 275 m/s2. Thus the acceleration due to gravity on the sun is 30 times greater than on the earth. Hence, the weight of the man on sun is greater than the weight of the man on the earth.

VII. Numerical problems.

1) Calculate the speed with which a satellite moves if it is at a height of 36,000 km from the Earth’s surface and has an orbital period of 24 hr (Take R = 6370 km)   [Hint: Convert hr into seconds before doing calculation]

Ans:

Given that, h = 36000 km, T = 24 hours = 24*60*60 = 86400 seconds

R = 6370 km

The time period of satellite is given by,

Time period T = distance covered/ orbital velocity

= 2πr/ v

T = 2π (R + h)/ v

86400 = 2* 3.14*(6370 + 36000)/ v

86400 = 266083.6/v

V = 266083.6/ 86400

V = 3.0796 km/s = 3079.6 m/s

This is the orbital velocity of the satellite with which it moves in a circular orbit around the earth’s surface.

2) At an orbital height of 400 km, find the orbital period of the satellite.

Ans:

Given that, h = 400 km, R = 6370 km, G = 6.673*10-11 Nm2kg-2, M = 5.972* 1024 kg

The orbital velocity of satellite is given by,

The time period of satellite is given by,

V = √GM/(R + h)

Where, G is the gravitational constant

M is the mass of the earth

R is the radius of the earth

Orbital velocity v = √6.673*10-11*5.972* 1024/ (6370 + 400)

V = √39.85*1013/6770* 103

V = √0.005886    * 105

V = 0.07672 * 105 m/s = 7.6 km/s

Time period T = distance covered/ orbital velocity

= 2πr/ v

T = 2π (R + h)/ v

T = 2* 3.14 * (6370 + 400)/7.6

T = 42515/ 7.6 = 5594 seconds

T = 5594/ 60 minutes = 93 minutes

Thus, the orbital period of satellite is 93 minutes.

Here is your solution of Tamilnadu State Board Solution Class 9 Science Chapter 9 Universe

I hope it will help you to solve your problems & I really appreciate you for being concerned with us.

Updated: May 26, 2021 — 3:05 pm