physics paper 5 help needed urgently

[evilish62]

how are we supposed to plot the error bars ? help someone

[123]

Dude!! have i got the site for u     : http://www.rit.edu/cos/uphysics/graphing/graphingpart1.html#errorbars
Just read thru the whole site!
Man this site has helped me soo much when i did my physics paper 5 ....u doin CIE Alevel right???
I didn't have a clue about these annoying bars!! even the stupid A level physics txtbooks didn explain dem...so i researched for a long time and found that best site for graphin!! Some stuff on it is not needed just see notes on paper5  at end of physics syllabus...it says the stuff needed...

PS: If u liked the site then give me some Rep...
Hope it helped

[evilish62]

thanks alot !! tell me, suppose if i want to plot error bars on the x axis... so my point would be (x,y),+error in x , -error in x ? but suppose the error is 0.4 ? wouldnt that error bar be really really small? and i was solving mayjune 07 p5, and the errors keep on getting bigger, so the error bars are supposed to get bigger as well?

[Valensi101]

Wow that link is useful, because tomorrow is my Phys P5 exam, and I didn't know anything about error bars. Thanks

[123]

thanks alot !! tell me, suppose if i want to plot error bars on the x axis... so my point would be (x,y),+error in x , -error in x ? but suppose the error is 0.4 ? wouldnt that error bar be really really small? and i was solving mayjune 07 p5, and the errors keep on getting bigger, so the error bars are supposed to get bigger as well?

hmm...yeah that happens...error bars are supposed to get bigger....
u know why?? think about the % error...does it get > or < if u take a small to large measurement?

[evilish62]

--------------------------------------------------------------------------------
i still need some more help. see, when i draw the error bars , theres not much difference between my worst acceptable line and best fitt line.. moreover i there any quicker way of finding the gradients of the lines, cuz its extrememely nerve-wrecking to count each and everypoint accurately. its also very hard to plot the error bars .. what am i doing wrong?

[Lana Wolf]

--------------------------------------------------------------------------------
i still need some more help. see, when i draw the error bars , theres not much difference between my worst acceptable line and best fitt line.. moreover i there any quicker way of finding the gradients of the lines, cuz its extrememely nerve-wrecking to count each and everypoint accurately. its also very hard to plot the error bars .. what am i doing wrong?

i really dont why ure stressing soo much on error bars...lol///
they're really simple....
okay..so in the 1st part of the question you'll calculate some value with its errors..
Then for the graph...
1) Plot all the normal points without the error bars...
2) Then the errors which you obtained for the calculated values..insert them into ur graph...
eg..if you hav an error of 0.5 for a value of 2.7...on your graph plot 0.5 above and below ur 2.7 point..so one will be at 3.2 and another will be at 2.2..(y- co ordinates)...
Simple enuf...

Now..your worst and best fit line...

1) Draw a line passing thru most of the points or if not thn atleast within all error bars...
2) Then on your graph start from one point and its error bar...start ur worst fit line from one error bar to your final points error bar..
The idea is to show the maximum deviation tht one can obtain from the best fit line...this way ur line passes thrru all the error bars...is correct and is very much different from your best fit line...

And for an easier way of finding the gradient... i dunno hw to actually explain it in writing..
but i can tell you one thing..
Start your gradient lines from one x or y axis co-ordinate you already know..so now atleast you dont find to find 4 diff values...

I hope you understood what i'm trying to say..cuz im really not that good at teaching/explaining stuff ..lol  

[Lana Wolf]

thanks alot !! tell me, suppose if i want to plot error bars on the x axis... so my point would be (x,y),+error in x , -error in x ? but suppose the error is 0.4 ? wouldnt that error bar be really really small? and i was solving mayjune 07 p5, and the errors keep on getting bigger, so the error bars are supposed to get bigger as well?

your error bars wont always be the same...
they change with the uncertainties in ur values..
so, yes they can either be too small or too large....