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Physics: Post your doubts here!

Mairaxo

Mairaxo

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rehan751 said:
Yeah practical sucks :p . How was your P4? And what about my original question, can I get an A* if I get A in P4 and P5.
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I know its hard!! umm honestly u cant b sure about that. It all depends on the marks not the grades. Sometimes if u get an A in all papers u still end up with an overall A instead of the expected A* :p But dont worry ISA well do it ;) My p4 was good :) what bout yours? I really wanted to discuss though! so do u wanna discuss or u forgot our answers? ;P
 
Mairaxo

Mairaxo

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zackle09 said:
Can someone PLEEASEEE help me with these questions?

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s12_qp_12.pdf

4,18,22 25 26 28 35 38
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Q 22 - 1st of all calculate mass* 6.02*10^23. this gives u the mass of all atoms in the crystal. then find the volume by dividing the mass u calculated by density. density=mass/volume. Then divide volume by 6.02*10^23. and find its cube root :)

Q25- Umm i guess extension will be the same as it obeys hookes law. Not sure though :/

Q26 - speed=2d/t. distance is muliplyd by 2 as its reflected so it travels the same distance twice. speed is that of light. so (2*150)/3*10^8 will give u 1 microsecond.

Q28- the two points are very apart by almost 1 full wave. Half wave apart is 180 degree but here the separation is greater so its 270.
Q35- sorry cant explain ! bad at this chap :/
Q38 - Just use a similar value for all resistors like 5ohm and calculate the combined resistance. If u use 5ohm then circuit 1 has resistance of 2ohm, 2 has 3 ohm. and 3 has 3.75 ohm :)
 
R

rehan751

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Mairaxo said:
I know its hard!! umm honestly u cant b sure about that. It all depends on the marks not the grades. Sometimes if u get an A in all papers u still end up with an overall A instead of the expected A* :p But dont worry ISA well do it ;) My p4 was good :) what bout yours? I really wanted to discuss though! so do u wanna discuss or u forgot our answers? ;P
Click to expand...


Mine went good as well. Well we can discuss, but we'll be going off-topic.
 
Mairaxo

Mairaxo

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Rahma Abdelrahman said:
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w10_qp_12.pdf
I know I have a lot of doubts.. will be really grateful for help :D
Q5, 8, 14, 22, 25, 26, 33, and, 34
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Q5- x is 0.44. Add uncertainties. U get 0.03. (0.03/0.44)*100 = 7%
Q8- find speed in both places. speed between X and Y = 40/12 and speed between Y and Z is 40/6. Then acceleration = change in velocity/time. so find the change in velocity and divide it by the average of time i.e. (12+6)/2
Q14- find the hypotenuse force 1st. 200/sin30. that will give u 400N. Then 400*1.5 gives 600J. Add frictional force and u get 750J.
Q22- Answer is a because it needs to have high sensitivity for small masses and low for high masses. The spring having smaller k stretches more and larger k stretches less. smaller k should be in the rigid box so it stretches till a certain extent. Hence small masses will make it stretch but when a large mass is present the small k spring will b stopped by the rigid box while the larger k will stretch less and show lower sensitivity.
Q25 & 26- sorry i suck in this chap :/
Q33- answer is d as the current had to be 2 not 1.8. just add both resistance and divide voltage by it to fins current. for example for a resistance was 10. so 2+10=12. then V=IR so I=12/12=1
Q34- votage decreases linearly so its supposed to be b :)
 
Oliveme

Oliveme

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TaffsAsLevel said:
Hey hey can you help me again, this time it's paper 5 june 2007 :confused::sick:(n) , if for example l is a quantity in cm with an uncertainty +- 0.4, so what happen to the uncertainty if they ask for l^2
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Let's assume l is 10.2 (+- 0.4). When l is squared, we square the two extreme points and subtract them to get uncertainty in the l squared value.
10.2^2 = 104.04 and uncertainty = (10.2+0.4)^2 - (10.2-0.4)^2
= 10.6^2 - 9.8^2
= 112.36 - 96.04 = 16.32
So, we have 104.04 (+- 16.32).
Hope you get it.
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TaffsAsLevel
I hope you see this as soon as possible. There's a small, teeny mistake here. You divide the 16.32 by 2.
So the uncertainty will actually be 16.32/3 = (+-8.16)
If we don't divide it by 2, it's actually tell us the whole range over which the value can lie because of the error.
So, the uncertainty will be (+-8.16). Just remember to always divide by two.
 
Tkp

Tkp

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Oct nov 12(12)-30,38
Oct nov 12(13)-11,16,28(do we need to memorise this),30,35
Oct nov 12(11)-6,11,14,35
 
Tkp

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Rahma Abdelrahman

Rahma Abdelrahman

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Ahmedraza73 said:
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w10_qp_12.pdf
Can any one help me with the Question No:7,15,22...
Please anyone :(
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Mairaxo said:
Q22- Answer is a because it needs to have high sensitivity for small masses and low for high masses. The spring having smaller k stretches more and larger k stretches less. smaller k should be in the rigid box so it stretches till a certain extent. Hence small masses will make it stretch but when a large mass is present the small k spring will b stopped by the rigid box while the larger k will stretch less and show lower sensitivity.
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Q7--> First of all the acceleration is negative because "g" which is acceleration due to gravity is negative and constant... The small pulse is as u know at the time the ball hits the ceiling... Imagine it like that: when it hits the ceiling and bounces back its acceleration increases...there is a simple concept to know that the answer is D, simply because the puls is approximately in the middle of the line... not towards the end as in C
Q15--> F=mg , and F=kv as mentioned in the question... so, mg=kv ....... so, v=(mg)/k
then you use KE=1/2 (m(v^2) ) and substitute v with (mg)/k.. u will get the expression in D
 
Rahma Abdelrahman

Rahma Abdelrahman

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Mairaxo said:
Q5- x is 0.44. Add uncertainties. U get 0.03. (0.03/0.44)*100 = 7%
Q8- find speed in both places. speed between X and Y = 40/12 and speed between Y and Z is 40/6. Then acceleration = change in velocity/time. so find the change in velocity and divide it by the average of time i.e. (12+6)/2
Q14- find the hypotenuse force 1st. 200/sin30. that will give u 400N. Then 400*1.5 gives 600J. Add frictional force and u get 750J.
Q22- Answer is a because it needs to have high sensitivity for small masses and low for high masses. The spring having smaller k stretches more and larger k stretches less. smaller k should be in the rigid box so it stretches till a certain extent. Hence small masses will make it stretch but when a large mass is present the small k spring will b stopped by the rigid box while the larger k will stretch less and show lower sensitivity.
Q25 & 26- sorry i suck in this chap :/
Q33- answer is d as the current had to be 2 not 1.8. just add both resistance and divide voltage by it to fins current. for example for a resistance was 10. so 2+10=12. then V=IR so I=12/12=1
Q34- votage decreases linearly so its supposed to be b :)
Click to expand...

Q8--> Can u please explain again? I think there is something wrong
Q14--> Why is the hypotenuse force 200/sin30, why not 200*sin30 ?
Q33--> Didn't get what u meant...
Q34--> What I thought was.. Lower resistivity means decreasing V.. I know that.. so, Why the answer is not D? Why the voltage decreases within th the material,? yes it shd decrease from the first one to the second... not through the first.. u got what I meant right?
Thanks for ur help but please clarify the above points..THANK YOU :)
 
Rahma Abdelrahman

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Oishee Asif

Oishee Asif

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I've got quite a lot of problems. Would be extremely grateful if anyone could explain as much as they could.

O/N '10: P12 -- 22, 25, 27, 28
O/N '10: P11 -- 11, 34
O/N '09: P11 -- 10, 14, 15, 22, 28
M/J '09: P1 -- 9, 10, 11, 13, 15, 18

Sorry for any inconvenience in advance. :(
Requesting to be answered as soon as possible?

--Thank you, Oishee x
 
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