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CBSE Class 9 Answered

we know that space is vacuum then how did the stares, sun and the other heavenly bodies form?
Asked by shweta mondal | 22 Jun, 2013, 01:54: PM
answered-by-expert Expert Answer
The space is now a vacuum but initially, when the planets and solar system were still forming, it was not a vacuum. It is believed that billions of years ago, it was a hot ball of gases. Though this has not been absolutely proved, but this is most widely accepted and explained through big bang theory. 
 
The Big Bang theory is the prevailing cosmological model that describes the early development of the Universe.According to the theory, the Big Bang occurred approximately 13.798 ± 0.037 billion years ago,which is thus considered the age of the universe. After this time, the Universe was in an extremely hot and dense state and began expanding rapidly. After the initial expansion, the Universe cooled sufficiently to allow energy to be converted into various subatomic particles, including protons, neutrons, and electrons. Though simple atomic nuclei could have formed quickly, thousands of years were needed before the appearance of the first electrically neutral atoms. The first element produced was hydrogen, along with traces of helium and lithium. Giant clouds of these primordial elements later coalesced through gravity to form stars andgalaxies, and the heavier elements were synthesized either within stars or during supernovae.
Answered by | 23 Jun, 2013, 08:41: AM

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CBSE 9 - Physics
boxes a and b each of mass 2 kg having dimension 20 cm to 10 cm into 8 cm and 40 cm into 30 cm and to 15 January respective at kept on a horizontal surface as shown the figure the ratio of pressure accepted by box a on the surface accepted by box be on the surface is take g 10 m per second
Asked by arushiarushi921 | 11 Oct, 2023, 08:45: PM
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CBSE 9 - Physics
write a Newton's 2law , derive an expression for F equals to Ma
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Asked by vomtimittagurupriya | 29 Sep, 2023, 05:52: PM
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CBSE 9 - Physics
solve this problem
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Asked by kunaljat51 | 24 Jul, 2022, 10:25: PM
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CBSE 9 - Physics
a bus accelerates at 2m per second for first 10 second after the start and retards at 1m per second for next 10 second find the total distance covered by the bus
Asked by komalpoonia636 | 16 Jun, 2022, 02:07: PM
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CBSE 9 - Physics
Questions 23-25 are based on the information given below. Read the information and answer the questions that follow:A bob of mass ‘m’ is suspended by a string, g be the acceleration due to gravity the bob.When the bob is stationary, the tension ‘T’ in the string is T=mg.When the bob is pulled up with an acceleration ‘a’ the tension in the string is given by T= m (g + a)When the bob is allowed to move down with an acceleration ‘a’, the tension T in the string is given byT= m (g –a)  
Asked by avishisanghai | 20 Feb, 2022, 05:19: PM
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CBSE 9 - Physics
The weight of a boy on the surface of earth is 294N. Find its mass.
Asked by charvi | 26 Nov, 2021, 06:27: PM
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CBSE 9 - Physics
A block of wood is kept on a horizontal table the mass of the wooden block is 6 kg and its dimensions are 10 into 10 into 10 what is the pressure exerted by the wooden block on the table
Asked by aanchishraddha | 16 Nov, 2021, 09:27: PM
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CBSE 9 - Physics
A boy of mass 45 kg running 6 m/s jumps onto a 30 kg trolley moving in the same direction at 1.5 m/s. Their common velocity will be: A. 4.0 m/s B. 4.2 m/s C. 6.5 m/s D. 8.3 m/  
Asked by nishitatrambadia | 21 Oct, 2021, 09:38: AM
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CBSE 9 - Physics
Unbalanced force can also change the shape,size of the body as Balanced force do
Asked by anuragyvidya | 28 Sep, 2021, 12:47: PM
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CBSE 9 - Physics
what is linear momentum ?
Asked by frusbJusyktsnis | 17 Sep, 2021, 12:03: AM
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