A2 Physics | Post your doubts here

[Mobeen]

and thanks alot for all the help i recieved from every 1...

good luck ! and thanks for your help too

 

[SkyPilotage]

calculate current in 6 kiloohm resistor

Whats the answer, how did you solve it. I think you need the thermistor resistace?

 

[SkyPilotage]

November 2011 / 43 / Question 2 a) I thought the question said they were calibrated correctly. Please explain both points in mark scheme!

Question 1 b) When do we use g.p.e = k.e and Fg = centripetal force.
If we used weight = centripetal force here, why wouldnt it work?

 

[Jonathan127]

Jazakallah brother

But why did

Here it is:
From Part i) The Intensity that is reflected back from the muscle bone boundary is 0.331 i.e 0.331 x 0.389 I

The key to this part is that you have to deduce the Intersity reflection coefficient from part ii).
When the ultrasound reaches the surface of the muscle, 0.661 will be reflected and 0.389 will pass through ----> 0.331 x 0.389 x 0.389 I = 0.05 I

But why did you multiply (0.389^2 I ) x (0.331 ?

 

[SkyPilotage]

But why did
But why did you multiply (0.389^2 I ) x (0.331 ?

becuase it will pass through twice so 0.389 ^ 2 , and 0.331 percent is reflected back

 

[hassam]

Whats the answer, how did you solve it. I think you need the thermistor resistace?

oh yea 1.5 kilo ohm

 

[Mobeen]

November 2011 / 43 / Question 2 a) I thought the question said they were calibrated correctly. Please explain both points in mark scheme!

Question 1 b) When do we use g.p.e = k.e and Fg = centripetal force.
If we used weight = centripetal force here, why wouldnt it work?

we cant use centripetal force because there is NO centripetal force .. the rock is at rest at the surface !

 

[SkyPilotage]

we cant use centripetal force because there is NO centripetal force .. the rock is at rest at the surface !

yeah, true. dunno whats wrong with me lol . thanks
Question 2 a ) please?

 

[Mobeen]

yeah, true. dunno whats wrong with me lol . thanks
Question 2 a ) please?

calibration has been done according to the linear change of temperature ... but both the quantities 'donot change linearly' so calibration has no effect . . thermometer linear change ke hisaab se calibrate kiya hai par resistance linearly change ho he nai rhi ! get it ?

 

[Mobeen]

so where did everybody go ?

 

[SkyPilotage]

calibration has been done according to the linear change of temperature ... but both the quantities 'donot change linearly' so calibration has no effect . . thermometer linear change ke hisaab se calibrate kiya hai par resistance linearly change ho he nai rhi ! get it ?

ok how about ci) 50.00 + 273.15 = 323.15
why not 323.2 , shouldnt it be 4 s.f??? because the values given are 4 s,f. WHy is the answer 5 s,f?

 

[KaiserFury]

Hi guys,

Please, I need help with a few questions.

http://www.xtremepapers.com/CIE/ind... Level/9702 - Physics/&file=9702_w07_qp_4.pdf
Can anyone tell me how to do number 10 (c)?

http://www.xtremepapers.com/CIE/International A And AS Level/9702 - Physics/9702_s11_qp_41.pdf
What is the answer of Number 6 (b)(ii)?

http://www.xtremepapers.com/CIE/ind... Level/9702 - Physics/&file=9702_s03_qp_4.pdf
And can someone explain number 2 (a) and (b) in this exam?

Please help if you can. I greatly need it.

Jazakom Allah Khairan.

 

[angelicsuccubus]

Hi guys,

Please, I need help with a few questions.

http://www.xtremepapers.com/CIE/index.php?dir=International A And AS Level/9702 - Physics/&file=9702_w07_qp_4.pdf
Can anyone tell me how to do number 10 (c)?

http://www.xtremepapers.com/CIE/International A And AS Level/9702 - Physics/9702_s11_qp_41.pdf
What is the answer of Number 6 (b)(ii)?

http://www.xtremepapers.com/CIE/index.php?dir=International A And AS Level/9702 - Physics/&file=9702_s03_qp_4.pdf
And can someone explain number 2 (a) and (b) in this exam?

Please help if you can. I greatly need it.

Jazakom Allah Khairan.

Ill reply for each one seperately cause my laptop is being uber-slow right now.

For s03 --q2 a) when water is evaporating at a constant temperature, there is no change in k.e but the molecules must overcome the intermolecular forces.. they move away from each other and so their potential energy increases. Internal energy is p.e + k.e, so internal energy is increasing if p.e is increasing.

Stretching a wire is the same story. When you stretch the wire, you make the atoms and electrons rearrange and move away from each other so the p.e increases.

 

[Mobeen]

ok how about ci) 50.00 + 273.15 = 323.15
why not 323.2 , shouldnt it be 4 s.f??? because the values given are 4 s,f. WHy is the answer 5 s,f?

in the question the temperatures are given to two d.p so we will give the answer to 2 d.p

 

[angelicsuccubus]

Hi guys,

Please, I need help with a few questions.

http://www.xtremepapers.com/CIE/index.php?dir=International A And AS Level/9702 - Physics/&file=9702_w07_qp_4.pdf
Can anyone tell me how to do number 10 (c)?

http://www.xtremepapers.com/CIE/International A And AS Level/9702 - Physics/9702_s11_qp_41.pdf
What is the answer of Number 6 (b)(ii)?

http://www.xtremepapers.com/CIE/index.php?dir=International A And AS Level/9702 - Physics/&file=9702_s03_qp_4.pdf
And can someone explain number 2 (a) and (b) in this exam?

Please help if you can. I greatly need it.

Jazakom Allah Khairan.

2b) very hard to explain.. it barely makes sense to me..

 

[angelicsuccubus]

are all of you going to go sleep soon? ...

 

[Mobeen]

Hi guys,

Please, I need help with a few questions.

http://www.xtremepapers.com/CIE/index.php?dir=International A And AS Level/9702 - Physics/&file=9702_w07_qp_4.pdf
Can anyone tell me how to do number 10 (c)?

http://www.xtremepapers.com/CIE/International A And AS Level/9702 - Physics/9702_s11_qp_41.pdf
What is the answer of Number 6 (b)(ii)?

http://www.xtremepapers.com/CIE/index.php?dir=International A And AS Level/9702 - Physics/&file=9702_s03_qp_4.pdf
And can someone explain number 2 (a) and (b) in this exam?

Please help if you can. I greatly need it.

Jazakom Allah Khairan.

ok so s03 Q2:
(a)
when water freezes particles lose energy ! so no increase internal energy
stone is falling in vaccum so i dont think there would any change in internal energy , so again no increase in internal energy
when water evaporates particles GAIN energy so increase in internal energy
when wire is streched its particles move from there original position so i guess increase in potential energy so increase in internal energy !
cross for first two and tick for last two

 

[JJHOLIC]

approximately few hours til our physics exam! good luck all of you guys!! hope you guys rock it! if you guys have any tips are doubt can you please share with us? thank you!!!

 

[Mobeen]

Hi guys,

Please, I need help with a few questions.

http://www.xtremepapers.com/CIE/index.php?dir=International A And AS Level/9702 - Physics/&file=9702_w07_qp_4.pdf
Can anyone tell me how to do number 10 (c)?

http://www.xtremepapers.com/CIE/International A And AS Level/9702 - Physics/9702_s11_qp_41.pdf
What is the answer of Number 6 (b)(ii)?

http://www.xtremepapers.com/CIE/index.php?dir=International A And AS Level/9702 - Physics/&file=9702_s03_qp_4.pdf
And can someone explain number 2 (a) and (b) in this exam?

Please help if you can. I greatly need it.

Jazakom Allah Khairan.

i explained w07 q10c earlier on this trend . . you can find it there ..

 

[user]

Thanks so much!

go through the graphs in the file attached...it helped me