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Help with Physics AS PRACTICALS

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lisahamed

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SALAM all :) i had some doubts with the procedures of the paper... would be very grateful if anyone could help out, thnx in advance :D
1.How to justify the number of significant figures
2.How to answer the questions "Explain whether your results support the suggested relationship". Do we find the percentage difference of "k" by dividing by any one of the values of calculated "k" or the average of the 2 values of calculated "k"
3.How do we estimate the percentage uncertainity?
Any other help with the practical paper would be appreciated :D thnx again
 
Gémeaux

Gémeaux

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It would be better if you could post a question that asks these. It'd be easier to answer each part that way with an example than to give generalized statements :)
 
syedhaider

syedhaider

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lisahamed said:
SALAM all :) i had some doubts with the procedures of the paper... would be very grateful if anyone could help out, thnx in advance :D
1.How to justify the number of significant figures
2.How to answer the questions "Explain whether your results support the suggested relationship". Do we find the percentage difference of "k" by dividing by any one of the values of calculated "k" or the average of the 2 values of calculated "k"
3.How do we estimate the percentage uncertainity?
Any other help with the practical paper would be appreciated :D thnx again
Click to expand...
Simply divide the error part to the actual value and multiply by 100
 
Gémeaux

Gémeaux

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lisahamed said:
i'm so sorry i dont have the readings for that particular paper :( .... i'm typing the ones that i do have from another year.. its http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w07_qp_32.pdf
2.b)ii) 12.2
c) ii) h=100cm..... t=0.7
d) ???? (not sure how to find it)
f) ii) d=8cm..... h= 100cm...... t=0.5s
g) ?? (not sure how to do it )
thanx again :D it means a lot to me
Click to expand...
Hope you wouldn't mind if I use my readings for this one :). It'd be easier for me.
Q2) (b)(ii) d= 9.3 cm
(c)(ii) h= 100cm, t= 0.97 s
(d)%age uncertainty= ( 0.02/0.97)/100 = 2.1%
(e) v = s/t = 100/0.97 = 103.1 cm/s
(f)(ii) d= 6.8 cm, h= 100cm, t=0.72s, v= 138.9 cm/s
(g) (for my readings)
d1= 9.3 v1= 103 v*d=957
d2=6.8 v2=138 v*d=945
Yes, they do. When d is more, v is lesser and vice versa, as the other factor (h) is same for each experiment. The constant v*d is almost same for both. The difference may only be because of experimental errors.
(h)(i) 1)Hard to see when cone hits the floor
2)Fewer readings taken.
3)Difficult to measure diameter as the cone is flexible.
4)If there is a draught(current of air), readings will vary.
(ii) 1) Take more readings and plot a graph.(this goes for most of the practicals :p)
2)Turn off any fans nearby.
3)Time over a greater distance.
4)Use more tape to balance the cone.
 
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lisahamed

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Gémeaux said:
Hope you wouldn't mind if I use my readings for this one :). It'd be easier for me.
Q2) (b)(ii) d= 9.3 cm
(c)(ii) h= 100cm, t= 0.97 s
(d)%age uncertainty= ( 0.02/0.97)/100 = 2.1%
(e) v = s/t = 100/0.97 = 103.1 cm/s
(f)(ii) d= 6.8 cm, h= 100cm, t=0.72s, v= 138.9 cm/s
(g) (for my readings)
d1= 9.3 v1= 103 v*d=957
d2=6.8 v2=138 v*d=945
Yes, they do. When d is more, v is lesser and vice versa, as the other factor (h) is same for each experiment. The constant v*d is almost same for both. The difference may only be because of experimental errors.
(h)(i) 1)Hard to see when cone hits the floor
2)Fewer readings taken.
3)Difficult to measure diameter as the cone is flexible.
4)If there is a draught(current of air), readings will vary.
(ii) 1) Take more readings and plot a graph.(this goes for most of the practicals :p)
2)Turn off any fans nearby.
3)Time over a greater distance.
4)Use more tape to balance the cone.
Click to expand...

thanx again for taking your time to do this! :D
btw at d) whr did the "0.02" come from?
and at g) dont we have to calculate the percentage difference of "k" here?.... and in other such question if we do need to find the percentage difference, should we divide the difference of the 2 "k"s divided by the average value of "k" and thn multiply by 100?
 
Gémeaux

Gémeaux

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lisahamed said:
thanx again for taking your time to do this! :D
btw at d) whr did the "0.02" come from?
and at g) dont we have to calculate the percentage difference of "k" here?.... and in other such question if we do need to find the percentage difference, should we divide the difference of the 2 "k"s divided by the average value of "k" and thn multiply by 100?
Click to expand...
I'm glad it helped :D Np.
Oh sorry, I forgot to mention. That is the least count. For uncertainty, divide the least count of your instrument by the reading you get.
In questions like (g), yes, that is what you ought to do in most of the cases, but I found it difficult doing that so did this here.
Yes, for that method, do what you just wrote. The answer is within 10%, your readings are reliable.
 
L

lisahamed

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Gémeaux said:
I'm glad it helped :D Np.
Oh sorry, I forgot to mention. That is the least count. For uncertainty, divide the least count of your instrument by the reading you get.
In questions like (g), yes, that is what you ought to do in most of the cases, but I found it difficult doing that so did this here.
Yes, for that method, do what you just wrote. The answer is within 10%, your readings are reliable.
Click to expand...
thank you soooo much agn! :D and is the least count for stop watch "0.02"? if it is... thn is it for the analogue one or the digital?
btw " i am not sure if i'd be called social..... i just like u a lot :D " ( heard it somewhr? ;) :D )
 
Gémeaux

Gémeaux

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lisahamed said:
thank you soooo much agn! :D and is the least count for stop watch "0.02"? if it is... thn is it for the analogue one or the digital?
btw " i am not sure if i'd be called social..... i just like u a lot :D " ( heard it somewhr? ;) :D )
Click to expand...
My pleasure :D :D
Umm.. actually it isn't always 0.02 sec. This depends on the instrument itself. There may be those with a least count of 0.2s (generally a good analogue) or with as much as 1s (a cheaper analogue one).
Ask your lab assistant what it is for the stopwatch you use.
:LOL: Thankyouu. (getting it only now, here :p )
 
L

lisahamed

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Gémeaux said:
My pleasure :D :D
Umm.. actually it isn't always 0.02 sec. This depends on the instrument itself. There may be those with a least count of 0.2s (generally a good analogue) or with as much as 1s (a cheaper analogue one).
Ask your lab assistant what it is for the stopwatch you use.
:LOL: Thankyouu. (getting it only now, here :p )
Click to expand...
thanks for all of it again :D :D
 
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