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Physics: Post your doubts here!

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Azfar94

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PHYSICS P5: plz tell me how to know the appropriate number of s.f and d.p for filling up the table in question 2?
 
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
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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

Tkp

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