Physics: Post your doubts here!

[Mohammed salik]

the first one is stationary and second one is progressive

Ohhhhhhh Okk.. This is what i was Missing.. The first one in http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_w13_qp_21.pdf Is Transverse,,! Thanx Mann.. NOw i compleely Get it!

 

[Suchal Riaz]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s10_qp_22.pdf

Q4 c)

Why λ/4, why not λ/6 or λ/8...etc.
Explain please?

at lowest frequency the first harmonic is made which is 1/4 λ in case of closed pipe
so L=1/4 λ so λ=4L
you can't make a wave smaller than this because there must be a node at closed end and antinode at open end

 

[Suchal Riaz]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s10_qp_22.pdf

Q4 c)

Why λ/4, why not λ/6 or λ/8...etc.
Explain please?

for smallest case there is only one node and antinode so:

distance b/w antinode and node is 1/4 λ

 

[Usman Chughtai]

http://papers.xtremepapers.com/CIE/...vel/Physics (9702)/9702_s12_qp_23.pdfMay/June 2012 paper 23
question 1 c(ii) part 1

Veactor triangle one

help please

 

[randomcod]

http://papers.xtremepapers.com/CIE/...and AS Level/Physics (9702)/9702_s08_qp_2.pdf
Q6 all Powers please!! Dunno how to do it

 

[mehria]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s08_qp_2.pdf
Q6 all Powers please!! Dunno how to do it

(a) P=V^2/R
R=V^2/P = (240)2/(1.5 x 10^3)
=38.4 ohms

(b)
when the powers r in series then we will add their reciprocals n when they r in parallel then we will add their values...
1. there will be no current so no power will generate
2. when S2 is closed then current will choose the low resistance path n will only flow through one heater.. so 1.5kW
3. all of them r closed.. no current is passing through B.. so we will simply add the powers that r in parallel with eachother.. 3 kW
4. the current is passing through A and B... so we will add the reciprocals of the powers n the ans will be 0.75 kW
5. Current is passing through all the heaters so... 0.75 + 1.5 = 2.25 kW

 

[Fahm Deen]

May/June 2011 Paper-23 6.(b) and c.(iv)...
Can anyone please draw the graphs of the waves and
Explain ASAP!!

 

[Mohammed salik]

(a) P=V^2/R
R=V^2/P = (240)2/(1.5 x 10^3)
=38.4 ohms

(b)
when the powers r in series then we will add their reciprocals n when they r in parallel then we will add their values...
1. there will be no current so no power will generate
2. when S2 is closed then current will choose the low resistance path n will only flow through one heater.. so 1.5kW
3. all of them r closed.. no current is passing through B.. so we will simply add the powers that r in parallel with eachother.. 3 kW
4. the current is passing through A and B... so we will add the reciprocals of the powers n the ans will be 0.75 kW
5. Current is passing through all the heaters so... 0.75 + 1.5 = 2.25 kW

MashAllah !

 

[mehria]

MashAllah !

 

[mehria]

May/June 2011 Paper-23 6.(b) and c.(iv)...
Can anyone please draw the graphs of the waves and
Explain ASAP!!

the peaks are curved not pointy like the one i've drawn in diagram 1....
for progressive wave the shape doesn't chnge...
for stationary after T/4 the wave becomes straight

 

[Fahm Deen]

the peaks are curved not pointy like the one i've drawn in diagram 1....
for progressive wave the shape doesn't chnge...
for stationary after T/4 the wave becomes straight

Can u explain the stationary wave thing with a bit detail.

 

[Usman Chughtai]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s12_qp_23.pdfMay/June 2012 paper 23
question 1 c(ii) part 1

Veactor triangle one

help please

kindly someone answer this one too

 

[waleed302]

http://papers.xtremepapers.com/CIE/...and AS Level/Physics (9702)/9702_w04_qp_2.pdf
Q6 c HELP!

 

[MiniSacBall]

http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_s10_ms_23.pdf

Q1 a ii)
How to do it i mean apart from adding 0.02, why do we add 0.01, is it because of the +-1 digit.

 

[waleed302]

kindly someone answer this one too

 

[MiniSacBall]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w04_qp_2.pdf
Q6 c HELP!

Well power = rate of work done / energy consumed / energy lost
Here they are asking for which has higher rate of energy loss.
So if you have drawn the curve of component R.
You will notice that P.d (V) across C is much greater than R, at any given current.
And if you remember P = IV, thus Power for C is higher than R.
Thus the energy lost (dissipated) is higher in C than R.

 

[waleed302]

Well power = rate of work done / energy consumed / energy lost
Here they are asking for which has higher rate of energy loss.
So if you have drawn the curve of component R.
You will notice that P.d (V) across C is much greater than R, at any given current.
And if you remember P = IV, thus Power for C is higher than R.
Thus the energy lost (dissipated) is higher in C than R.

But isn't the resistance of C decreasing with voltage? Why would the PD through it be greater than in R? Also, isn't the current through R constant? Why would there be a 'curve' for R?

 

[unique111]

the peaks are curved not pointy like the one i've drawn in diagram 1....
for progressive wave the shape doesn't chnge...
for stationary after T/4 the wave becomes straight

If it says .25T then phase difference will be 45 degree?

 

[waleed302]

If it says .25T then phase difference will be 45 degree?

90 degrees I think.

 

[unique111]

90 degrees I think.

Please, explain to me this.

the peaks are curved not pointy like the one i've drawn in diagram 1....
for progressive wave the shape doesn't chnge...
for stationary after T/4 the wave becomes straight