Physics: Post your doubts here!

[ashcull14]

V1= 5000/ (5000+5000) x 2 = 1V then V2= 3000/ (3000 + 2000) x 2 = 1.2 so V1 - V2 = -0.2 so C

thnk u

 

[ashcull14]

 

[Paresh]

Please mail @ [email protected] if someone knows about physics p34 ...

 

[Asad Moosvi]

Hey. In physics paper 3 (practical), how do I prove whether a mathematical relationship is supported or not by calculating two values of k? Can anybody help me out here?

 

[ShreeyaBeatz]

Hey. In physics paper 3 (practical), how do I prove whether a mathematical relationship is supported or not by calculating two values of k? Can anybody help me out here?

Simple as this:
1)You are asked to find out the %uncertainty of(say x) in the one of the question
2)you are also asked to find two values of k (k1 and k2) in one of the question
Now,
suppose you got %uncertainty of x as 20%. Then you find k1+ 20% of k1 AND k1-20% of k1
This is the range
If your value of k2(found in 2) matches it, THE RELATION IS SATISFIED
in most of the questions, it is satisfied.
I hope this helped!
Good luck. Light and luck bless you!

 

[Asad Moosvi]

Simple as this:
1)You are asked to find out the %uncertainty of(say x) in the one of the question
2)you are also asked to find two values of k (k1 and k2) in one of the question
Now,
suppose you got %uncertainty of x as 20%. Then you find k1+ 20% of k1 AND k1-20% of k1
This is the range
If your value of k2(found in 2) matches it, THE RELATION IS SATISFIED
in most of the questions, it is satisfied.
I hope this helped!
Good luck. Light and luck bless you!

I'm still a little confused.

The part that I don't get is this:

"Now, suppose you got %uncertainty of x as 20%. Then you find k1+ 20% of k1 AND k1-20% of k1
This is the range"

 

[Thought blocker]

Paper 34 - I haven't practiced a single experiment. :'(
Help me someone :'(

 

[ShreeyaBeatz]

I'm still a little confused.

I made the language simple. Take a little bit more time.
step 1 and 2 you dont have to worry. It will already be in your previous answers. they will also make you find k1 and k2, in the previous question.

now just simply put (suppose you got 20%)
Solve k1+ (20%of k1) =
solve k1- (20% of k1)=

does your value of k2(already found in previous question) lie between this?
If yes, it satisfies.

Tell me where you're confused. Take time to read

 

[Asad Moosvi]

I made the language simple. Take a little bit more time.
step 1 and 2 you dont have to worry. It will already be in your previous answers. they will also make you find k1 and k2, in the previous question.

now just simply put (suppose you got 20%)
Solve k1+ (20%of k1) =
solve k1- (20% of k1)=

does your value of k2(already found in previous question) lie between this?
If yes, it satisfies.

Tell me where you're confused. Take time to read

Does it matter if k1 is the smaller one or the larger one?

 

[Asad Moosvi]

I made the language simple. Take a little bit more time.
step 1 and 2 you dont have to worry. It will already be in your previous answers. they will also make you find k1 and k2, in the previous question.

now just simply put (suppose you got 20%)
Solve k1+ (20%of k1) =
solve k1- (20% of k1)=

does your value of k2(already found in previous question) lie between this?
If yes, it satisfies.

Tell me where you're confused. Take time to read

Can I just calculate the percentage difference between the two k's and if it's greater than the percentage uncertainty calculated earlier then it's not supported? And if it's less than or equal to percentage uncertainty calculated earlier, it is supported. Is this essentially the same thing?

 

[Asad Moosvi]

Paper 34 - I haven't practiced a single experiment. :'(
Help me someone :'(

How do you choose a sensible scale and draw the line of best fit? This always takes me a while.
Also, could you look at my previous post and tell me whether what I've said is correct or not. I'd really appreciate it.

 

[Wolfgangs]

http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_w13_qp_11.pdf

I need your help in few (or many XP) questions. They are Q5,9,11,14 and 30.

 

[NIM]

guyzz need help!!!
http://papers.xtremepapers.com/CIE/...and AS Level/Physics (9702)/9702_w07_qp_1.pdf
18, 19, 37
http://papers.xtremepapers.com/CIE/...and AS Level/Physics (9702)/9702_w06_qp_1.pdf
2, 6, 12, 15, 36
http://papers.xtremepapers.com/CIE/...and AS Level/Physics (9702)/9702_s09_qp_1.pdf
2, 9, 13, 21, 26, 31, 33

 

[NIM]

help with question 7,33,34 and 40 plz!
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s07_qp_1.pdf

i m nt so sure abut 7 and 34
q 33
Sp = (5/10) * 2= 1 V
for voltage at Q = (2/5) * 2 = 0.8
for V2 = 2-0.8 = 1.2
V1 - V2
1 - 1.2 = -0.20V

q 40
for finding the acceleration with lowest speed you have to divide no of protons with atomic mass
A. H ... 1/1 = 1
B. He ... 2/4 = 0.5
C. Li ... 3/7 = 0.43
D. Be ... 4/9 = 0.44
C has the lowest speed so C would be the answer.

 

[Wolfgangs]

http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_w13_qp_11.pdf

I need your help in few (or many XP) questions. They are Q5,9,11,14 and 30.

 

[ZaqZainab]

guyzz need help!!!
http://papers.xtremepapers.com/CIE/...and AS Level/Physics (9702)/9702_w07_qp_1.pdf
18, 19, 37
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w06_qp_1.pdf
2, 6, 12, 15, 36
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s09_qp_1.pdf
2, 9, 13, 21, 26, 31, 33

i will help you with w07 and w06 i havent done 2009 yet
w007
Q18
Surface pressure=100kPa
Pressure=dgh
surface height = 100000/(1030*9.81)=9.897 meters
now at 450kPa
450000/(1030*9.81)=44.535
so below surface=44.535-9.897=34.6

Q19 you need to know this learn this!

Q37 nuclear process like alpha or beta decay the proton number changes no option saying proton number proton is a nucleon

W06
Q2 Energry=mgh=kgm^2 s^-2
lets see what the first option says
Ft=ma*t=kgms^-1 nope not correct
Fvt=mavt=kg*ms^-2*ms^-2*s= kgm^2s^-2 yup correct thats it B is the answer

Q6 V = IR
R =V/I = 8/1 = 8 ohms
change in R/R = change in V/V + change in I/I
change in R = 8(.2 + .4) = 2
Therefore (8+- 2) ohms

Q12 momentum always conserved
mv before=mv after
1000*5=10*x
x=500

Q15 since both the forces are 10
cos(30)*20 gives the upward force=17.32
now resultant 17.32-10=7.32

Q36 Kirchhoff first law
sum of current entering a point=sum of current leaving
I2=20.2+10.6=30.8
I1+10.6=10.8

 

[Kamihus]

Paper 34 - I haven't practiced a single experiment. :'(
Help me someone :'(

Dw you can get many marks even without touching the apparatus. In first question ask the supervisor to set-up the apparatus if you don't have any idea (you'll get 2 marks deducted for it though). Change the values and you'll get the readings. Draw a graph and calculate gradient and draw line of best fit, these are in every practical. Read some marking schemes and examiner reports and you'll get some idea. For the second question you'll get marks for just finding the percentage uncertainties and writing correct significant figures. If you have no idea how to do it just write something closer to the value given like if its written take 50 cm write something close to it. Write subsequent values accordingly that look sensible and do the following calculations. You can write the uncertainties and the improvements anyway and just read some ms to know when to write what.

 

[Asad Moosvi]

Dw you can get many marks even without touching the apparatus. In first question ask the supervisor to set-up the apparatus if you don't have any idea (you'll get 2 marks deducted for it though). Change the values and you'll get the readings. Draw a graph and calculate gradient and draw line of best fit, these are in every practical. Read some marking schemes and examiner reports and you'll get some idea. For the second question you'll get marks for just finding the percentage uncertainties and writing correct significant figures. If you have no idea how to do it just write something closer to the value given like if its written take 50 cm write something close to it. Write subsequent values accordingly that look sensible and do the following calculations. You can write the uncertainties and the improvements anyway and just read some ms to know when to write what.

Hey I need help with a part from the second question. Where you have to show whether or not the relationship is supported by calculating two values of k. I've asked this before, but I'm still confused! Different people are telling me different things, this has just made it worse. You seem like you'd know this. Please help me!

Here, use this paper to explain. http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_w11_qp_34.pdf

 

[NIM]

i will help you with w07 and w06 i havent done 2009 yet
w007
Q18
Surface pressure=100kPa
Pressure=dgh
surface height = 100000/(1030*9.81)=9.897 meters
now at 450kPa
450000/(1030*9.81)=44.535
so below surface=44.535-9.897=34.6

Q19 you need to know this learn this!

Q37 nuclear process like alpha or beta decay the proton number changes no option saying proton number proton is a nucleon

W06
Q2 Energry=mgh=kgm^2 s^-2
lets see what the first option says
Ft=ma*t=kgms^-1 nope not correct
Fvt=mavt=kg*ms^-2*ms^-2*s= kgm^2s^-2 yup correct thats it B is the answer

Q6 V = IR
R =V/I = 8/1 = 8 ohms
change in R/R = change in V/V + change in I/I
change in R = 8(.2 + .4) = 2
Therefore (8+- 2) ohms

Q12 momentum always conserved
mv before=mv after
1000*5=10*x
x=500

Q15 since both the forces are 10
cos(30)*20 gives the upward force=17.32
now resultant 17.32-10=7.32

Q36 Kirchhoff first law
sum of current entering a point=sum of current leaving
I2=20.2+10.6=30.8
I1+10.6=10.8

Thnx a lot dude it did help me a lot

 

[Kamihus]

Hey I need help with a part from the second question. Where you have to show whether or not the relationship is supported by calculating two values of k. I've asked this before, but I'm still confused! Different people are telling me different things, this has just made it worse. You seem like you'd know this. Please help me!

Here, use this paper to explain. http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w11_qp_34.pdf

You subtract the smaller value of k from the bigger one, then divide them by the bigger one, although I'm not entirely sure which value to divide. If its less than the percentage uncertainty its supported if its not then simply write its not supported rather than it has an inverse relation.