ANSWER IN BRIEF
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- Explain the theory of formation of our Solar System.
ANS: It is believed that the universe was formed due to Big Bang. After the big bang the sun was surrounded by a cloud of gases. These clouds were slowly converted into rocks due to contraction. These rocks kept on colliding with one another and during this process they either got broken or fused together to form bigger structures which we call planets. Thus, the present solar system came into existence.
- Define Solar system and write the names of the planets in the ascending order of their distance from Sun.
ANS:Our solar system consists of the Sun, nine planets revolving around the sun, 91 satellites revolving around planets, more than 1 lakh asteroids, comets, etc.
The planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto. - Explain : Corona.
ANS:Sun is a sphere of hot gases.
The 400 km thick, bright layer around the sun is known as 'photosphere'.
The layer beyond photosphere is invisible normally because the gases are very hot and less dense. During solar eclipse, this layer becomes visible like a 'crown'. this is called 'Corona'. - Mention the names and the characteristics of terrestrial planets.
ANS:Mercury, Venus, Earth and Mars are terrestrial planets. Their characteristics are as follows:
- Terrestrial planets have structure similar to that of the earth.
- They have less number of satellites(moons).
- Their atmosphere is very thin.
- Terrestrial planets have structure similar to that of the earth.
- Describe in brief how the atmosphere protects life on earth.
ANS:The atmosphere on earth protects life in the following way:
- Atmosphere protects us from meteors as they burn out due to friction before reaching the earth's surface.
- The ozone layer of atmosphere blocks ultraviolet rays of solar radiation from reaching the surface and protects us from its harmful effects.
- The natural Green House Effect due to gases like carbon dioxide and methane keeps the atmosphere warm enough to sustain life.
- Atmosphere protects us from meteors as they burn out due to friction before reaching the earth's surface.
- Write a note on Mars.
ANS:
- Earth's neighbour mars is reddish in colour.
- Its surface has large valleys, mountains and dry rivers.
- Its atmosphere is extremely thin (1% of earth's atmosphere) and mainly contains carbon dioxide with traces of nitrogen and argon.
- The 'Path Finder' mission of 1997 indicated the presence of flowing water on mars in the past.
- At present the probability of existence of life on mars is negligible.
- 'Phobos' and 'Demos' are its two moons (satellites).
- Earth's neighbour mars is reddish in colour.
- Write the names of jovian planets and mention their characteristics.
ANS:Jupiter, Saturn, Uranus, Neptune and Pluto are Jovian planets. Their characteristics are:
- They are beyond the orbit of mars.
- Their composition is similar to that of Jupiter.
- They are bigger in size but have less density.
- They are mainly made up of hydrogen, helium and ammonia.
- Their moons are bigger in size.
- Most of them possess rings around them.
- They are beyond the orbit of mars.
- Write a few points on Jupiter.
ANS:
- Considering the distance from sun, Jupiter is the fifth planet of our solar system.
- It is about 1400 times bigger than earth and is the biggest planet of the solar system.
- It is a luminous planet with some bright and hazy belts of brownish colour.
- It can be seen with naked eyes.
- It has 39 satellites (moons).
- Considering the distance from sun, Jupiter is the fifth planet of our solar system.
- Write a note on Saturn.
ANS:
- Saturn is the second largest planet of our solar system.
- It is 850 times bigger than earth.
- It is believed that saturn is completely made of hydrogen.
- Its crust might be made up of fluid hydrogen whereas the core might be made up of solid hydrogen.
- It has three beautiful luminous rings.
- It has 30 satellites.
- Saturn is the second largest planet of our solar system.
- Write a few words about Neptune.
ANS:
- Neptune is bluish planet with two luminous and hazy rings.
- Its core contains silicate rocks and ice.
- The upper crust has methane ammonia and water in ice form.
- It has 8 moons.
- 'Triton' and 'Nerid' are its well-known moons.
- It cannot be seen with naked eyes.
- Neptune is bluish planet with two luminous and hazy rings.
- 'Night-sky changes everyday.' Explain.
ANS:
- The earth takes 23 hours 56 minutes to complete one rotation about its axis whereas one day is made up of 24 hours.
- Due to this the sun rises four minutes earlier than its rising time on the previous day.
- During this 4 minutes there is 1° angular displacement of stars in the celestial sphere.
- Thus, stars appear for about 6 months continuously (180° angular displacement) and then disappear for remaining 6 months.
- This shows that the Night-sky changes every moment, though the change apparent only after a long period and for a short period(like 1 day) there is no noticeable change in the position of stars.
- The earth takes 23 hours 56 minutes to complete one rotation about its axis whereas one day is made up of 24 hours.
- Write a few points on Milky Way.
ANS:
- The galaxy in which our solar system is situated is called the Milky Way. Milky Way appears as a milky belt stretching from North to South during dark night when the sky is clear.
- Milky Way is spiral in shape when viewed from the top. When viewed from the sides, it is seen bulging at the center and tapered towards the ends.
- The diameter of Milky Way is about 1 lakh (0.1 million) light years and the thickness of the middle (bulging) part is about 15000-20000 light years.
- Sun (and therefore the solar system)is located at about 30000 light years away from the galactic center.
- The sun completes one revolution around the galactic center in 22.5 crore (225 million) years at the speed of 250 km/s.
- The galaxy in which our solar system is situated is called the Milky Way. Milky Way appears as a milky belt stretching from North to South during dark night when the sky is clear.
- Expalin the principle of rockets.
ANS:Rockets work on the principle of Newton's third law of motion.
When the fuel in the rocket engines burns, gases produced during combustion come out of the nozzle with very high momentum and the rocket is pushed upward. - Mention the properties of a rocket fuel.
ANS:A rocket fuel should have the following properties:
- Its combustion rate should be high.
- It should not be explosive in nature.
- It should produce large amount of gases at high temperature and pressure.
- Its combustion rate should be high.
- Mention the two major disasters of space shuttles.
ANS:The two major disasters of space shuttles are :
- In 1986, the space shuttle Challenger exploded and seven astronauts on board died.
- In February,2003, the space shuttle Columbia met with an accident a few minute before its landing in which the astronaut of Indian origin, Kalpana Chawla, died along with others.
- In 1986, the space shuttle Challenger exploded and seven astronauts on board died.
- What is an artificial satellite ? What is it equipped with ?
ANS:A man-made automatic system launched in space with a special purpose and which revolves around the earth is called an artificial satellite.
It is equipped with transponders, high-resolution cameras, radiometer, solar panels and necessary fuel. - Describe the use of artificial satellites in communication.
ANS:Following are the uses of artificial satellites in communication :
- For telecommunication(telephone).
- For television transmissions.
- For radio networks.
- For computer networks(internet).
- For countrywide classrooms.
- For teleconferencing.
- For telecommunication(telephone).
- Explain the installation of artificial satellite by space shuttle.
ANS:
- A space shuttle carries a satellite to be launched in space with other instruments as payload.
- After the space shuttle has attained its required height in space, it continues to revolve around the earth in an orbit.
- Once it stabilizes properly in its orbit, a robotic arm in its upper part opens up.
- It holds the satellite to be installed and releases it in the space in its orbit.
- After the launching of satellite is over, the shuttle starts its return journey.
- A space shuttle carries a satellite to be launched in space with other instruments as payload.
- Explain how the space shuttle is brought back from space.
ANS:
- After the completion of tasks in space the pilot directs the space shuttle towards the earth.
- Though the outer surface of space shuttle is made up of special alloys to withstand extremely high temperatures, the speed of the space shuttle is controlled carefully while entering the earth's atmosphere.
- The direction of the entry to the atmosphere is also critical.
- Computers (on the earth) control the journey of space shuttle till it is a few meters above the earth's surface.
- The pilot then takes control and makes the smooth landing of the space shuttle possible like an aeroplane.
- Thus, a space shuttle is brought back to the earth.
- After the completion of tasks in space the pilot directs the space shuttle towards the earth.
- Describe the use of satellites for Remote Sensing.
ANS:
- Remote sensing is the method by which information about a substance, matter or a phenomenon can be obtained using scientific instruments without direct contact with them.
- Remote sensing satellites can carry out geological survey of metallic ores in the earth's crust, water resources, agricultural resources, changes in forests, etc.
- These satellites can be used to know about crop yield and diseases spread in crop.
- They find use in oceanography and study of motion of fish.
- The sensors of these satellites cover area of 10 square meter to 6400 square meter and send information to the earth station.
- Remote sensing is the method by which information about a substance, matter or a phenomenon can be obtained using scientific instruments without direct contact with them.
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