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Universe - 1 (Class X)

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Why do planets not collide with each other while revolving around the sun?

  1. Because they have their own elliptical orbits

  2. Because they have their own circular orbits

  3. Because they repel each other

  4. Both (2) and (3)


Correct Option: A
Explanation:

Because they have their own definite elliptical path known as orbit

Matter in the core region of the sun is in ____________ state.

  1. solid

  2. liquid

  3. gaseous

  4. plasma


Correct Option: D
Explanation:

 Matter in the core region of the sun is in plasma state.

Which of the following options is/are true?

  1. Pluto is a dwarf planet.

  2. All planets revolve in their respective orbits due to centripetal force.

  3. Sun contains 99.86% mass of the solar family.

  4. All of the above


Correct Option: D
Explanation:

 Pluto is a dwarf planet. Sun contains 99.86% mass of the solar family. All planets revolve in their respective orbits due to centripetal force.

Why is it difficult to observe the planet Mercury?

  1. Because of its small size

  2. Because it is at a large distance from Earth

  3. Because of the glare from the sun

  4. Both (1) and (2)


Correct Option: C
Explanation:

It is difficult to observe the planet Mercury because of the glare from the Sun. 

Venus is the ________ planet and it rotates from ______.

  1. dullest; west to east

  2. dustiest; west to east

  3. brightest; east to west

  4. dullest; east to west


Correct Option: C
Explanation:

Venus is the brightest planet and it rotates from east to west.

Mars is also called ___________ and it has ______ natural satellites.

  1. the blue planet; two

  2. the red planet; three

  3. the grey planet; three

  4. the red planet; two


Correct Option: D
Explanation:

Two natural satellites revolve around Mars. It is also called the red planet.

Which of the following statements is/are true?

  1. Neptune is an outer planet.

  2. Neptune has a large number of moons.

  3. Neptune is at maximum distance from the sun.

  4. All of the above


Correct Option: D
Explanation:

Neptune is an outer planet. It has a large number of moons. It is at maximum distance from the sun.

Which of the following statements is not true?

  1. Uranus rotates from east to west.

  2. Uranus has a highly tilted rotational axis.

  3. Uranus in its orbital motion appears to roll on its side.

  4. Uranus can be seen through small telescopes.


Correct Option: D
Explanation:

Uranus can be seen only through large telescopes.

Which of the following statements is/are true?

  1. Saturn has a large number of satellites.

  2. Saturn appears yellowish in colour.

  3. Rings of Saturn can be seen with naked eyes.

  4. Both (1) and (2)


Correct Option: D
Explanation:

Saturn has a large number of satellites and it appears yellowish in colour.

Why does Earth appear blue-green from space?

  1. Due to reflection of light from water and landmass

  2. Due to refraction of light from water and landmass

  3. Due to transmission of light from water and forests

  4. Everything looks blue and green from space


Correct Option: A
Explanation:

Due to reflection of light from water and landmass, Earth appears blue-green from space.

The gap between the planets Mars and Jupiter is occupied by small objects that revolve around the sun. They are known as _____.

  1. meteors

  2. asteroids

  3. venus

  4. shooting stars


Correct Option: B
Explanation:

Asteroids fill the gap between Mars and Jupiter.

_______ comet appears after every 76 years.

  1. Linear

  2. Borrelly's

  3. Halley’s

  4. Hartley's


Correct Option: C
Explanation:

Halley’s comet appears after every 76 years.

What do you mean by meteorites?

  1. Small meteors are known as meteorites.

  2. Meteors that reach the surface of the earth before evaporating completely are called meteorites.

  3. Meteors that crash into the surface of the earth at night time only are called meteorites.

  4. Meteors that reach the surface of the earth after cooling down in the cold upper reaches of the atmosphere are called meteorites.


Correct Option: B
Explanation:

Meteors that reach the surface of Earth before evaporating completely are known as meteorites. 

Why do meteors glow?

  1. Chemical reactions in the core of meteors heat them up, liberating light.

  2. Friction due to atmosphere heats them up, liberating light.

  3. Gravitational force of Earth heats them up, converting potential energy to heat energy.

  4. Entering Earth's magnetic field ionises their particles and they start glowing.


Correct Option: B
Explanation:

The friction due to the atmosphere heats them up and they glow.

Which of the following statements is true about the density of the planet Saturn?

  1. Its density is more than that of water.

  2. Its density is less than that of water.

  3. Its density is equal to that of water.

  4. We do not know anything about its density.


Correct Option: B
Explanation:

Its density is less than that of water.

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