A2 Physics | Post your doubts here

[histephenson007]

????

look at my previous answer again, I edited it

 

[angelgirl:)]

how u got 25*10^8?

work done= area of the triangle
1/2 * base * height
work done is P*delta volume
so-----> 1/2* 25*10^8* ((2*10^-4)-(8*10^-4)) {as the arrow is going from R to P}
===> -840J

 

[histephenson007]

????

In an earlier question, it asked the total energy change in PQRP which is zero. So, the sum of the third column should be zero. Since we already know that the first two are -360and +720,

-360+720+ x = 0
So, x = -360
Then
u = q + w
-360 = 480 + x
so, x = -360 - 480 = -840

 

[angelgirl:)]

work done= area of the triangle
1/2 * base * height
work done is P*delta volume
so-----> 1/2* 25*10^8* ((2*10^-4)-(8*10^-4)) {as the arrow is going from R to P}
===> -840J

base is 25*10^5...isnt it?

 

[larina]

base is 25*10^5...isnt it?

ohh sorrry its 28*10^5

 

[iris987]

please help me with A2 physics booklet

 

[SkyPilotage]

@histephenson007 and SkyPilotage! How the hell did you guys prepare for physics. You guys know answers to everything!

thats quite an over-exaggeration dont you think? Most of my doubts were answered over here... Lots of people helped me. I still have alot of unanswered doubts.
Plus, im only taking physics, so I had a whole month to study, and I still have lots of confusions!

GOT IT!!!!!!!!!!

In an earlier question, it asked the total energy change in PQRP which is zero. So, the sum of the third column should be zero. Since we already know that the first two are -360and +720,

-360+720+ x = 0
So, x = -360
Then
u = q + w
-360 = 480 + x
so, x = -360 - 480 = -840

true, thats the correct way to do it.

 

[leadingguy]

please help me with A2 physics booklet

what kind of help??

 

[iris987]

i am not comfortable with the third portion and is it important to learn the range of radio frequencies .

 

[smzimran]

i am not comfortable with the third portion and is it important to learn the range of radio frequencies .

No,
Just remember the trend which have higher frequencies and which have lower.

 

[user]

aoa wr wb! for applications, did you ppl practice questions from paper 6?

 

[smzimran]

aoa wr wb! for applications, did you ppl practice questions from paper 6?

Yes, I did some of them!
They are mostly questions that have been almost repeated in the late years

 

[iris987]

]How we should study PSTN

 

[histephenson007]

Hi everyone, I'm new here
Could someone please help me with these questions:

Q3 b) (iii) - I don't understand why the increase in internal energy is ∆U = 4.05 × 10^4 – 3050 = 37500 J . Because heat enters the system, so it makes sense that it is positive, but why is the work done on the system negative? I thought that work done by the system is negative.

Q6 c) (ii) I don't understand how to sketch that graph

Q3 b) iii) I think what you say is right. Work done on the system should be positive. Although I explain this from that perspective, I will try to make some sense by explaining it in an alternative way. If you just ignore the words for a moment,

We know the formula W = -P (dV) , where dV is delta volume.
We can write this as W = -P (V2 - V1)
When V2 > V1, dV is positive, hence Work done is negative.
When V2 < V1, dV is negative, hence Work done is positive.
In this case, V2 > V1, so we may say that the Work done is negative.

I think they did a mistake in typing that as work done on the system.

 

[ousamah112]

aoa wr wb! for applications, did you ppl practice questions from paper 6?

yes i did few days back..only medical and communication options.

 

[SkyPilotage]

i am not comfortable with the third portion and is it important to learn the range of radio frequencies .

No,
Just remember the trend which have higher frequencies and which have lower.

my advice to you, please do memorize at least frequencies. wavelengths can be found by v = lambda x frequency
"(l) Candidates should be able to recall the frequencies and wavelengths used in different channels of communication. "

Yes, I did some of them!
They are mostly questions that have been almost repeated in the late years

you mean paper 5? I didnt even look at it -_- .. do we have to?

]How we should study PSTN

That its the network that connect telephones together.
You should know about the trunk exchange and the international gateway exchange.
Thats basically it.

 

[RGBM211]

Use molar quantities where one mole of any substance is the amount containing a number of particles equal to the Avogadro constant.

??

 

[user]

my advice to you, please do memorize at least frequencies. wavelengths can be found by v = lambda x frequency
"(l) Candidates should be able to recall the frequencies and wavelengths used in different channels of communication. "

you mean paper 5? I didnt even look at it -_- .. do we have to?

That its the network that connect telephones together.
You should know about the trunk exchange and the international gateway exchange.
Thats basically it.

i meant paper 6...before 2007 there was no section B in paper 4 and instead there was a paper 6...

 

[OrlandoBloom<3]

My doubt has been ignored :/ someone please help !

 

[RGBM211]

LOL same here ^