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Biology; Chemistry; Physics: Post your doubts here!

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http://papers.xtremepapers.com/CIE/Cambridge International O Level/Physics (5054)/5054_w12_qp_12.pdf

Question number 7. Why is it D????
Question number 29.from x to y the resistance should be 6 only. Why is my answer wrong?
Question number 36. I so dont get this cro shit. :/
And how do you calculate the half life of isotopes?
Plus when a gas is heated it expands and the molecules more more often and hard with the container. Both are correct right?
this is correct if the volume does not change ...so pressure would increase...
 
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But if you look at question 15 in the same paper both options are given although the ms says that it doesn't expand.
molecules cannont expands....and according to the formula 1/2m(v)2:k.e when temperature increases the energy increases and hence the velocity(speed)of the molecus...as volume does not change the molecules cannot move further apart.........
 
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the answer is c simce it says tht i cm= 5ms... so in one complete wave there were 4 cm's....therefore 4*5 = 20 ms

So you mean that for calculating the time we have to cosider ONE wave ONLY? And one wave means 2 in phase points i.e one crest and one trough successively. Right?
 
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Alright I have the answer to this question
Muammar (mind the spelling) as right
Graphit contains non-covalent bonds known as Wan-der-Waal's forces of attraction
wow...he found the answer......no one in they brilliant mind could not have thought of this.......lol
 
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634553_xlarge.jpg
so is there a time tht both the valves are open....
 
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1% is way too less. It may cause shock or coma. Blood contains much more glucose. If it has only 1%, then how would it supply the immense amount of glucose in respiring cells
the question states name a tissue which would have much more thn 1%.......
 
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The resultant force in an object moving in a circle would be towards or away from the circle? If its towards i.e centripetal than what is the centrifugal?
 
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The resultant force in an object moving in a circle would be towards or away from the circle? If its towards i.e centripetal than what is the centrifugal?
inside the circle that is centripetal
there is no such thing as centrifugal force in pure physics, it is a non-scientific concept
 
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how hydrogen carbonate reacts with CO2,what is the equation and why its product is yellow in color?

Hydrogen Carbonate, from what I recall, is used in the Bio questions involving respiration/photosynthesis where you have to see if CO2 is being produced or used. Nothing more. You're not supposed to know the equations AFAIK. If it's a particular question that you've seen in a past paper, please link me to it.
 
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