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Biology; Chemistry; Physics: Post your doubts here!

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Assalamu Alaykum!
Well, I have the same doubts! : (
Voltage , pd and emf all have the same Si units ie Volts and the same formula i.e J/C(joule/coulomb charge).
What differs is that Voltage and pd is the conversion of Electrical Energy into other forms of electrical energy per coulomb. On the other hand emf is referred to energy supplied by some source. Its formula is work done over Q. Which when rewritten would again give you J/C.
 
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guys i need help please. bio past year m/j 2002 question 4.c
explain why the blood pressure in the left ventricles falls to zeroin the cardiac cycle, but the lowest blood pressure recorded in the arteries is about 10kpa.
answer :
i. (pressure falls to zero) because all blood expelled from ventricle
ii. (blood pressure falls to 1okPa) because elastic ffibres recoil.
iii. ref to smooth muscles qualified
iv. narrow diameter of capillaries/arterioles/small arteries
v, resistance to flow

i dont understand how they relate point ii-v to the low blood pressure in arteries. anyoneee can explain to meee ? thanks so much :)
Which paper is this question exactly from..?? Because no such question is there in O level june 2002 paper 2...
 
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help me out with this.
energy is needed to breakdown the proteins and starch and fats.in seed germination how the process of breaking down larger molecules start because there is no glucose at the start for respiration.
 
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Hello , can someone explain to me why is the answer A for this question:
28. All ammonium salts on heating with sodium hydroxide produce ammonia gas.
From which ammonium salt can the greatest mass of ammonia be obtained?
A 0.5 mol (NH4)3PO4
B 0.5 mol (NH4)2SO4
C 1.0 mol NH4Cl
D 1.0 mol NH4NO3
This is from O/N/04, thanks :)
 
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Hello , can someone explain to me why is the answer A for this question:
28. All ammonium salts on heating with sodium hydroxide produce ammonia gas.
From which ammonium salt can the greatest mass of ammonia be obtained?
A 0.5 mol (NH4)3PO4
B 0.5 mol (NH4)2SO4
C 1.0 mol NH4Cl
D 1.0 mol NH4NO3
This is from O/N/04, thanks :)

Ammonia is NH3

A has the greatest number of N and H atoms
 
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need notes for turning effect of forces exercise with complete solution some 1 help me plz plz plz:cry:
 
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Which element is most likely to be as an industrial catalyst?
A) Li
B) Cs
C) Rh
D) Po
Please give reason for Rh as ans.
 
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Out of these three opitions:
i) Cambridge O Level Physics 2012 by David Sang (Complete Cambridge))
ii) GCE 'O' Level Physics Matters
ii) Fundamental of physics for O level by Stephen Pople
Which one should I choose to read from. Which is the most descriptive book that covers the whole syllabus of 2013(or 2014) in a lucid and easy language.
Usually Physics matters is followed as it covers most, if not all, points. Although like all books it has got some mistakes. There are some topics not covered by this book whose good description you will find in Stephen Pople's book. Otherwise it's pretty good to follow as a text. As for the last one, I have heard that Stephen Pople's is not very descriptive.
Don't know about the first one :-/
 
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Can anyone pls help me out with IGCSE Biology June 2012 Paper 12 Q16.... the ans in the ms is A but I cant understand why..????? Pls help asap as i hv my exam tomo..!!:(
 
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Can anyone pls help me out with IGCSE Biology June 2012 Paper 12 Q16.... the ans in the ms is A but I cant understand why..????? Pls help asap as i hv my exam tomo..!!:(
Humid air contains a great deal of water vapour, so the concentartion gradient of water vapour between the surrounding air and the leaf is greatly reduced. And air can accept very little water vapour from plants.
 
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how shld study for biology as i am going to appear for may june 13 ...................pls help:confused:
 
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