Physics Practical ( Paper 3 ) Tips :)

[[Spy]]

im doing 31

[*Hope*]

Thanks spy!!
really appreciate it but i still don't get why do we take lower values?? reduce experimental errors..do we include them in our table??
plz explain further....Thanks and By the way +rep

[[Spy]]

Your Welcome Mate

if you look at the past papers, they often ask you to repeat the experiment with different values of a specific factor, length of thread/resistance for example. you should take a value just a bit lower so you'd see how it compares. and to have that value included in your readings. and By the way YOU SHOULD ALSO INCLUDE THE EXACT HALF WAY READING For example if the range given is 0.3-0.6 then you must include 0.45, yeah its not just anything you have to include specific things.
what do you mean "reduce experimental errors..do we include them in our table??"

thanks

[*Hope*]

i mean that if they ask us to take the lengths between 0.3 and 0.6, right u said to take 0.25 and 0.65, so do we include the 0.25 and 0.65 in our table of results or we include 0.3 and0.6 although we have used 0.25 and 0.65??

[[Spy]]

no no, you take six readings for example or whatever they ask you and you include this as a standard.

0.25
0.30
0.45
0.55
0.60
0.65
i included a value lower (25) a value higher (65) a value in the middle (45) and the values they asked for (30 and 60) you can include any number as a sixth preferrebly above the half

[*Hope*]

r u sure about it?? From where did u get this info??
it will be very useful if u can post the source of this info

[[Spy]]

my teacher, and he's been teaching a levels for 12 years. so i'd trust his word, and besides it sounds very logical, you can at least only use the actual values  (0.3 and 0.6) but you should use the middle value.

[*Hope*]

THANX LOADZ

[[Spy]]

your welcome

where's the +rep?

[A.T]

- also when doing your table record two readings, name them t1 and t2 for instance and then find the average. and use the AVERAGE when plotting.

can u elaborate this ?
what is t1 and t2

[*Hope*]

your welcome

where's the +rep?

i did give u one but dunno y not appearing
anywayz i'll give u another 1 after 2 hours have passed
listen do u noe how to calculate the uncertainties??

[[Spy]]

lets say you have to record the time taken for a pendulum to stop swinging, you should repeat each twice for each length..

for example, your recording the time taken for a 0.5 meter pendulum to stop, then you time it once, and twice. you get 10.51 and 10.75 then find find the average and use this as the time value for the length of 0.5 meter

then do the same for your other lengths

hope its clear?

[[Spy]]

i did give u one but dunno y not appearing
anywayz i'll give u another 1 after 2 hours have passed
listen do u noe how to calculate the uncertainties??

oh probably takes time to show, haha thanks

yeah its easy, the key is you ALWAYS add them, and they should be in PERCENTAGE Form. these two things are very important.

for example lets say you have the equation.Q=A*B^2 all over C^1/2

and A=1.3mm +/- 0.02
B= 2.8mm +/- 0.01
C= 0.8mm +/- 0.008

convert all to percentages first! for example A= 0.02/1.3 * 100 and do the rest for B and C
lets say for example you get A=1% and B=2% and C=1% (im too lazy to calculate )
so you plug them into the equation.
AND YOU ALWAYS ADD. but before that, any thing to the power of X, in uncertainties you multiply by the power. (because your adding them twice for instance if its squared you multiply by 2)
so for our equation. its 1+(2*2*(the power)) + 1*0.5(the power) as you can see its always ADD no matter what the equation is.

so your uncertainty is 1+4+0.5=5.5%. and if you want to find it as a value of the actual result. then use this equation. X/the value= 5.5/100

i hope its clear
                                       

[unknown 101]

oh probably takes time to show, haha thanks

yeah its easy, the key is you ALWAYS add them, and they should be in PERCENTAGE Form. these two things are very important.

for example lets say you have the equation.Q=A*B^2 all over C^1/2

and A=1.3mm +/- 0.02
B= 2.8mm +/- 0.01
C= 0.8mm +/- 0.008

convert all to percentages first! for example A= 0.02/1.3 * 100 and do the rest for B and C
lets say for example you get A=1% and B=2% and C=1% (im too lazy to calculate )
so you plug them into the equation.
AND YOU ALWAYS ADD. but before that, any thing to the power of X, in uncertainties you multiply by the power. (because your adding them twice for instance if its squared you multiply by 2)
so for our equation. its 1+(2*2*(the power)) + 1*0.5(the power) as you can see its always ADD no matter what the equation is.

so your uncertainty is 1+4+0.5=5.5%. and if you want to find it as a value of the actual result. then use this equation. X/the value= 5.5/100

i hope its clear
                                       

didnt understand anything!!! 

[[Spy]]

HAHAHAHAHAHAHA NASHAT, GO STUDY