Physics, Chemistry and Biology: Post your doubts here!

[ChrisChin]

Q1. a) av.speed= (v+u)/2
=15m/s
b) a=(v-u)/t
a=(20-10)/60
a=(1/6)m/s2
distance=ut+1/2at2
=(10*60)+1/2*(1/6)*(60)2
=600+300
=900m

Q2. t=(v-u)/a
t=(1100-600)/10
t=500/10
t=50h

Q3. t=(v-u)/a
t=(0-20)/-5
t=-20/-5
t=4s.

Answer to Q2 is wrong in terms of units. It should be 50 seconds, not 50 hours. Because the acceleration is 10km/h per second, not 10km/h per hour.

 

[A.H]

thank you all, that was really helpful.

 

[Iridescent]

Answer to Q2 is wrong in terms of units. It should be 50 seconds, not 50 hours. Because the acceleration is 10km/h per second, not 10km/h per hour.

Thanx 4 correcting me!

 

[ktc]

mayn steam iz also used to turn da rotator so dere iz use steam in hydro electric power station>>>>>>>>

hope dis helped ya 2 much extent>>>>>>>>

Steam is not used in hydroelectric power stations at all!

It’s the gushing water that turns the rotator – not steam [besides, it’s practically impossible ]

 

[Iridescent]

Heat is used in Thermal Power Stations

 

[ChrisChin]

Hey guys, Wassup?
Would you have a look at question no. 9 in paper 1 physics Nov. 2005?
I don't get how come hydroelectric power station isn't produced from steam?!

One more reply to this one.

Most types of power stations use a form of energy that produces heat. The heat itself cannot be used to turn the generators, because we need KE to turn turbines, not HE. So we use the heat to produce steam, which has KE (water has less volume than steam, and higher volume requirement in a fixed volume chamber produces pressure, which pushes the steam out at high velocity) and can turn the generators by pushing at the turbine blades. i.e., if there is heat, we make and use steam to turn the turbines.

Hydro in hydroelectric means water. Water can push a turbine blade directly because it can be made to rush through the turbine. Also, water has no HE to speak of, so we cannot make steam (which, by the way, requires a LOT of HE) to push the turbines. Besides, why convert it to steam, if we can already use the water itself AND gain efficiency at the same time?

I hope that helps you remember, and helps you to understand why we prefer to use water directly.

 

[A.H]

it helped more than u think.. really thanks

 

[A.H]

I have a problem in Chemistry paper 3: in Nov.06 Q 5 b ?!

 

[princessanum]

I have a problem in Chemistry paper 3: in Nov.06 Q 5 b ?!

i will try to help !!
so the question says tht how are the gases recycled?
Ans:If only 15 % of your reactants formed ammonia on one pass over the catalyst then you have to pass it over the catalyst a number of times. Each time extract the ammonia add more H2 and N2 and through again.
the other part says Only ammonia gas liquefies. Suggest an explanation for this.
Ans:as it is having the highest boiling point..

 

[areebaization]

URGENT!
Can somebody please tell me in physics 0625, do we have to learn ONLY the equations given in the syllabus?
Give me an accurate answer please!

 

[GetSomeLife]

URGENT!
Can somebody please tell me in physics 0625, do we have to learn ONLY the equations given in the syllabus?
Give me an accurate answer please!

ofcourse (accurate enuf???)


u hav to do EVERYTHING according to d syllabus...

 

[ktc]

URGENT!
Can somebody please tell me in physics 0625, do we have to learn ONLY the equations given in the syllabus?
Give me an accurate answer please!

If you’re asking whether the *equations given in the 0625 Physics syllabus* are the only equations you have to learn [nothing from outside the syllabus] – then yes.

But if you’re asking if the *only thing to learn* in the 0625 Physics syllabus are the equations – then no.

Here’s the whole syllabus [Go through it - it’ll help, a lot ]:-

 

[A.H]

URGENT!
Can somebody please tell me in physics 0625, do we have to learn ONLY the equations given in the syllabus?
Give me an accurate answer please!

well, yea sort of, you must be able to identify, explain, define, memorise all what the syllbus wants but its nt just about that you also have to practise the past papers.
This is the sort of questions you should be able to answer, and managing that isnt difficult at all, just solve them, if u faced any porblems I'll be pleased to help you... Is that detailed enough??

 

[areebaization]

hae guyz iz there any website from where we can get da notes of ATOMIC PHYSICS>>>>

Hey why don't you try watching videos at Khanacademy.org ?
Hope it helps

 

[Spirit95]

http://www.astarmathsandphysics.com/igcse_physics_notes_menu.html

This is a link with a lot of useful notes for almost every topic in the syllabus.

 

[ChrisChin]

URGENT!
Can somebody please tell me in physics 0625, do we have to learn ONLY the equations given in the syllabus?
Give me an accurate answer please!

If you just want to PASS, then the equations are fine. If you want an A*, you're going to need to do more than that. Pretend that you have to *teach* your fellow students. If you feel prepared to do that, then you may be able to get that A*. Good luck.

 

[Ahmed Khider]

Hey everyone i got my mocks coming up next month...any advices on how to prepare for them?

 

[areebaization]

If you just want to PASS, then the equations are fine. If you want an A*, you're going to need to do more than that. Pretend that you have to *teach* your fellow students. If you feel prepared to do that, then you may be able to get that A*. Good luck.

Okay so let me be clear i am doing EVERYTHING from the extended syllabus but what I wanted to ask was that do i need to know any other formulae?

 

[ChrisChin]

Okay so let me be clear i am doing EVERYTHING from the extended syllabus but what I wanted to ask was that do i need to know any other formulae?

Your Math formulas are occasionally useful, but I assume you already know them, so no.

 

[A.H]

when it says (in paper 6) draw a smooth line graph, does this mean to draw it with the rule? or just draw it smootly without it??