Physics: Post your doubts here!

[BreakingBad]

Q1(d)
HELP ME OUT!

Since it's in equilibrium:
Upward forces = Downward forces
and
Forces towards right ride = Forces towards left side.

Split T1 and T2 into their vertical and horizontal components. The use the information above to obtain 2 equations:

T1sin50 + T2sin40 = 7.5
and
T1cos50 - T2cos40 = 0

Solve them simultaneously and get your answer.

 

[sitooon]

Why gravitational force not cosidered ?
answer in MS : gravitational force << Fb of Fe
does it mean perpendicular?

 

[BreakingBad]

Why gravitational force not cosidered ?
answer in MS : gravitational force << Fb of Fe
does it mean perpendicular?

It actually means that the gravitational force is TOO small in comparison with Fb or Fa and hence, is negligible.

 

[periyasamy]

Q3
c) ii) M1/M2 is given as 3 and in the previous par we calculated that M1/M2 = R2/R1
Therefore R2/R1 = M1/M2 = 3
R2 = 3R1
R2 - 3R1 = 0 (is our first equation)
The total separation is 3.2 * 1o^11
Therefore, R1 + R2 = 3.2 * 10^11 (our equation 2)

Solve these 2 equations simultaneously:
R2 - 3R1 = 0
R2 + R1 = 3.2 * 10^11

R2 = 2.4*10^11
R1 = 8*10^11

There is no Q4 part (d).


Yes.

Thanks a lot..........

 

[snowbrood]

http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_w09_qp_42.pdf
why cant we calculate 2 c(ii)

 

[Saad Mughal]

just completed the As syllabus with Classified and yearly papers from 2001-2005. alhamdulillah. now i will do rest of the papers in april. its time to so further math. Saad Mughal

Anything in the AS syllabus that you found more complicated than the rest? Superposition?

 

[Hassan Ali Abid]

just completed the As syllabus with Classified and yearly papers from 2001-2005. alhamdulillah. now i will do rest of the papers in april. its time to so further math. Saad Mughal

Dont leave the past.pprs of phy till april ....solve them asap bcz at the end u wont get time to know ur weak areas and deficiencies....
P.s dont forget to look the questions of waves from pacific phy book bcz the trend of the questions from this topic is changed from 2013 onwards ...and lastly they are improving the difficulty level of phy pprs so dont take it easy .

 

[BreakingBad]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w09_qp_42.pdf
why cant we calculate 2 c(ii)

dU = q + w
dU = mc(dT) + pV
Volume can also be used instead of mass but 'c' is still not given.

 

[Suchal Riaz]

Dont leave the past.pprs of phy till april ....solve them asap bcz at the end u wont get time to know ur weak areas and deficiencies....
P.s dont forget to look the questions of waves from pacific phy book bcz the trend of the questions from this topic is changed from 2013 onwards ...and lastly they are improving the difficulty level of phy pprs so dont take it easy .

i did classified which include the questions of pacific. actually i have done 1970-2007 till now. i have to do further math thats why i have to leave physics. thanks for advice though

 

[Suchal Riaz]

Anything in the AS syllabus that you found more complicated than the rest? Superposition?

waves was a little bit complicated. most difficult were the old questions of electricity and waves. it took me 3 weeks to complete classified of waves. although newer questions are easy. physics is easy atleast of As Level. grating, interference and difraction are all easy once u have the concept. but the concept comes at the expense of a lot of time.

 

[Suchal Riaz]

Anything in the AS syllabus that you found more complicated than the rest? Superposition?

What about FM?

 

[snowbrood]

dU = q + w
dU = mc(dT) + pV
Volume can also be used instead of mass but 'c' is still not given.

why cant charles law v1/t1=v2/t2 pressure is kept constant. also the pv=nRT why cant we use any of these equation from both equations i get 120K and 140K i dont get it why is this wrong.

 

[Saad Mughal]

waves was a little bit complicated. most difficult were the old questions of electricity and waves. it took me 3 weeks to complete classified of waves. although newer questions are easy. physics is easy atleast of As Level. grating, interference and difraction are all easy once u have the concept. but the concept comes at the expense of a lot of time.

Yeah, I know, I've gone through the chapter twice. I have to practice past papers. It is the most 'complicated' chapter of AS Physics according to my teachers.

 

[Saad Mughal]

What about FM?

Not continuing it until I complete P3 Maths first.

 

[periyasamy]

Guys ,very confused with the internal energy part.Just want to ask something to clear it up.
1)1st of all when work is done on system is it +ve or -ve?
2)example

ice > water -------->steam

Guys,this conversion of ice to water to steam ?Is it all work done on system or by system.
Thanks a lot

 

[periyasamy]

Another question here guys,
i have a question that i got the answers from this forum long time ago.But i dont get 1 of the part in the working.
why in the 3 b part 2.there is a value of 8676 joule,isnt it suppose to be 8700,the answer for the 1st part.
Even the answer show the same thing.Help guys.Thanks a lot....

 

[BreakingBad]

why cant charles law v1/t1=v2/t2 pressure is kept constant. also the pv=nRT why cant we use any of these equation from both equations i get 120K and 140K i dont get it why is this wrong.

The question says that the volume is increased from 1.8 to 2.1. This is done by moving the piston and not by heating the cylinder because the question mentioned 'insulated' cylinder. Therefore, it doesn't make sense for the temperature to RISE (as it seems to do when using pV = nRT or v1/t1 =v2/t2) when the volume is increased. For that to happen, heat must be supplied and q=mc(dT) where 'c' is missing.

Guys ,very confused with the internal energy part.Just want to ask something to clear it up.
1)1st of all when work is done on system is it +ve or -ve?
2)example

ice > water -------->steam

Guys,this conversion of ice to water to steam ?Is it all work done on system or by system.
Thanks a lot

1) Work done on the system is negative.
Work done by the system is positive.
When you use the equation U = q - W

2)
Take a cylinder with insulated walls with a piston on one end. Let's assume you are pushing the piston. The gas is the system. You are the surroundings doing work on that system. Therefore, the work done on the gas is the work done by you (surroundings) and is positive. The work done by the gas in order to reduce it's volume is the work done by the system and is negative.

I didn't exactly understand the ice to water to steam part. It depends on the conditions. Try to elaborate.

Another question here guys,
i have a question that i got the answers from this forum long time ago.But i dont get 1 of the part in the working.
why in the 3 b part 2.there is a value of 8676 joule,isnt it suppose to be 8700,the answer for the 1st part.
Even the answer show the same thing.Help guys.Thanks a lot....

The answer of the first part IS 8676 J.
mc(dT) + mL

m =24/1000 kg
c = 2.1 * 10^3
dT = 15
L = 3.3 * 10^5

Substitute values and you'll get 8676, which will then be used in the second part.

 

[periyasamy]

Thank u breaking bad....Nvr mind for the ice part,i got ady.Thanks boss!!!

 

[sara kamal]

http://papers.xtremepapers.com/CIE/...and AS Level/Physics (9702)/9702_w06_qp_4.pdf

please explain Q4 part B....i m getting answer as 6 x 10^22 but its 6 x 10^24..

 

[BreakingBad]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w06_qp_4.pdf

please explain Q4 part B....i m getting answer as 6 x 10^22 but its 6 x 10^24..

Change in PE = GMm [1/(R+h1) - 1/(R+h2)]
Change in KE = 1/2m (v1^2 - v2^2)

Equate equations. m cancels. Substitute values of G, (R+h1), (R+h2), v1 and v2 and you'll get the correct answer.