Post by: Friends on May 18, 2010, 11:34:08 am
Post by: sabrina on May 18, 2010, 11:45:06 am
anyone with any tips plz share. the mcq's r usually very hard and i always make silly, supid mistakes. any suggestions r welcome.thanks in advance :)
Post by: matabd on May 18, 2010, 11:49:01 am
Lol, im doing the exam also tomorrow! Good Luck to everyone
Post by: Friends on May 18, 2010, 12:01:10 pm
Try and do all the PYQ's , Memorise all your formulas, Dont burn the midnight oil tonight.
Lol, im doing the exam also tomorrow! Good Luck to everyone
PYQ's??????
Post by: highly_ambitious on May 18, 2010, 12:07:05 pm
Post by: Friends on May 18, 2010, 12:19:59 pm
may/june 2003 q22 plzzz..
The Ans is "D".....
As middle spring is removed total extension becomes 1.5x (3x/2)
When load is doubled extension also doubles....
So the ans is 3x which is D... If u dont understand anything in this explaination tell me...
Hope this helps..
Post by: XaM!! on May 18, 2010, 12:22:37 pm
Post by: sabrina on May 18, 2010, 12:27:34 pm
Post by: Friends on May 18, 2010, 12:30:45 pm
tip is first do last 5 ques as they are the easiest ones... than do frm 20-28, they r of waves n r easy. these ques wont take much time... after that start frm 1st ques... try to solve a paper like this n see the time consumption... it wil help a lot. trust me...
I just checked 3 pastpapers nd ur trick worked....last 4-5 ques dead easy nd 20-28 also easy.....
wow never thought of it this way....thanx a lot....:)
Post by: halosh92 on May 18, 2010, 12:36:35 pm
The Ans is "D".....
As middle spring is removed total extension becomes 1.5x (3x/2)
When load is doubled extension also doubles....
So the ans is 3x which is D... If u dont understand anything in this explaination tell me...
Hope this helps..
could u plzz explain how u got the total extension???
and for parallel and series how do u calculate total extension and the total of constants -------------just a general question
Post by: highly_ambitious on May 18, 2010, 12:38:44 pm
The Ans is "D".....
As middle spring is removed total extension becomes 1.5x (3x/2)
When load is doubled extension also doubles....
So the ans is 3x which is D... If u dont understand anything in this explaination tell me...
Hope this helps..
how come does extension is 1.5x when the middle spring is removed. The extension is
Post by: Friends on May 18, 2010, 01:06:21 pm
how come does extension is 1.5x when the middle spring is removed. The extension iswhich is
. plz explain!
I will explain u with a example....
1) Force is directly propostional to extension.. So as force increses the extension also increase...
2) eg: let say the weight W exerts a force of 6N...So each spring pull 2N (6N/3springs)
Now let say we removed the middle spring.. So now each spring (2 springs) has to pull 3N (6N/ 2 springs) which is 1.5 times the original...
As u know force is directly propostional to extension the extension which is "x" with 3 springs becomes 1.5x with 2 springs...
Hope this will solve ur doubt...
Post by: sabrina on May 18, 2010, 01:17:29 pm
very interesting theory. i understood it perfectly now, though i never asked this doubt ;D
Post by: highly_ambitious on May 18, 2010, 01:27:05 pm
Post by: highly_ambitious on May 18, 2010, 01:40:56 pm
PYQ's??????
Past Year Questions ;D ;D ;D ;D
Post by: Friends on May 18, 2010, 01:45:38 pm
ny one plz solve m/j 2009 question 18...i think answer should be C but in mark scheme it is D...what's the reason plzz explain.
Anyone????? I also dont know......
Post by: halosh92 on May 18, 2010, 01:57:28 pm
Anyone????? I also dont know......
I THINK....maybe...from one side the liquid goes up so thats "h" and from the other side the liguid goes down by "h" so total is 2h
but still that doesnt make any sense right?? :S
Post by: Friends on May 18, 2010, 02:08:47 pm
I THINK....maybe...from one side the liquid goes up so thats "h" and from the other side the liguid goes down by "h" so total is 2h
but still that doesnt make any sense right?? :S
Thats what i initially thought but as u said it doesnot make sense i also rejected that idea but till now it is the only idea we have....
Post by: highly_ambitious on May 18, 2010, 02:40:08 pm
I THINK....maybe...from one side the liquid goes up so thats "h" and from the other side the liguid goes down by "h" so total is 2h
but still that doesnt make any sense right?? :S
lol...if we apply this logic then the difference in the height for two columns is still 'h' so P = rho.g.h . according to which answer should be C !!
still don't know the right ans...somebody plzz help in this question.
Post by: Joseph_COOL on May 18, 2010, 02:58:35 pm
Here is the attachment for the Question
Post by: Friends on May 18, 2010, 02:59:30 pm
lol...if we apply this logic then the difference in the height for two columns is still 'h' so P = rho.g.h . according to which answer should be C !!
still don't know the right ans...somebody plzz help in this question.
A wild guess....
I think they might me talking about hieght of water in rhs above lhs
I know its the same thing but with different view...
Post by: Joseph_COOL on May 18, 2010, 03:03:16 pm
Post by: halosh92 on May 18, 2010, 03:04:48 pm
Plz June 2008 Q28 with explanation
Here is the attachment for the Question
whenever they say for eg : 600 lines per m
then d= 1/600
same thing here
the formula is
n lamda= dsin thita
n=3
d=1/N
3 lamda = 1/N sin thita
3 lamda N = sin thita
got it?
Post by: matabd on May 18, 2010, 03:06:09 pm
What i think is that Since the RHS new pressure is Patm. - pgh and the LHS pressure is Patm+pgh. Thus the Increase is equal to RHS-LHS so you get 2pgh.
Also the Diffraction grating:
use dsintheta=nlambda
then u get sin Theta=3Lambda/d
they say that it has N lines per unit length. That means ur line spacing d = 1/N. Cos they said its N lines per Unit length, which can be said to be abt 1 metre. Putting that into the equation, sin Theta = 3LambaN
Post by: Joseph_COOL on May 18, 2010, 03:07:34 pm
Post by: Joseph_COOL on May 18, 2010, 03:10:53 pm
how about Q29 June 2008??
Post by: matabd on May 18, 2010, 03:11:49 pm
x=Lambda X d / a
d = distance from double slits
a=slit spacing
since x(fringe SPacing) is directly proportional to lambda, as Lambda is Halved, so is x therefore your new x= 1.5mm. However, your slit spacing is doubled. SInce X is inversely proportional to slit spacing, since a is doubled, x must be halved , and so your new x=0.75mm. Just move in steps
Post by: halosh92 on May 18, 2010, 03:12:48 pm
thanks very much halosh :D
ure welcome
Q29)
lambda= ax/D
700 * 10^-9 = [a * (3/1000) ]/D
( we divide 3 by 1000 to change it to m, and we multiply 100 by 10^-9 to change from nm to m)
D= [a * 0.003]/ (700 *10^-9)
this is D
now
labmda=ax/D
substitue that value of D in this formula
[350 * 10^-9 ] * ( a* 0.003)/(700 *10^-9) = 2ax
cancel out the "a" as its common on both sides
x= 0.00075 m *1000 = 0.75 mm
got it?
Post by: Joseph_COOL on May 18, 2010, 03:20:50 pm
Post by: halosh92 on May 18, 2010, 03:23:41 pm
thx
Post by: Joseph_COOL on May 18, 2010, 03:31:50 pm
Post by: Joseph_COOL on May 18, 2010, 03:37:52 pm
Post by: halosh92 on May 18, 2010, 03:44:56 pm
anyone plz Q22 and Q26 November O9
Q26) n lamda= d sin thita
its fallin at 90 degrees (normal) as they say so thita =90
sin 90= 1 ( check with ure calculator)
we have to find "n"
n * (450*10^-9) = 1/(300* 10^3)
(300 mm as i mentioned previously it would be 1/300 but because its mm so u have to change m to mm so 300 *10^3...so it would be 1/(300*10^3)
we dont consider sin 90 in the equation because its =1
anyways
when u solve the equation n=7.4
so basically u have 7 maximas..BUT..they asked for the total number of maximas
u have 7 maxima up and 7 maxima down thats 14...and dont forget the central main maxima where u find the white light on the centre of the screen thats a maxima
so 14 + 1= 15 maxima in toal
got it?
Post by: Joseph_COOL on May 18, 2010, 03:50:19 pm
Post by: halosh92 on May 18, 2010, 03:52:12 pm
thanks very much halosh u got an easy way of explanation :D :D
glad to help dude ;D ;D ;D
Post by: matabd on May 18, 2010, 03:53:16 pm
Lol i dont think i would know how to explain it easier. Thats what i think :( Sorry
Post by: halosh92 on May 18, 2010, 04:04:14 pm
anyone plz Q22 and Q26 November O9
Q22)Y.M=STRESS/STRAIN
stress=F/A
stress=F/pie (d/2)^2
stress=20/ ( pie *(([5*10^-4])/2)^2)
strain= stress/Y.M
strain = stress(the value we calculated above substitute here)/ (2*10^11)
starin= answer A
basically the question is asking for estension/original length which is nothing but strain
Post by: matabd on May 18, 2010, 04:06:01 pm
First use the formula E=Fl/ax (E= Young Modulus, F=Tension l = original length A=Cross sectional area and x=extension)
First find A
A=Pi/4 D^2
A=Pi/4 (5x10^-4)^2
A= 1.9635x10^-7
thus if u rearrange the formula you get x/l = F/AE
Yes ? just rearrange the above formula i gave you. Then u put in the values for F, A and E
so x/l = 20/(1.9635x10^-7)(2x10^11)
thus u get the fractional change in length, to get Percentage you want to multiply the value by 100.
So u get Answer B (x/l is just the fraction how it changes, we want to find the percentage of original length)
Post by: aldehyde1612 on May 18, 2010, 04:16:53 pm
Firstly for the Pressure One:
What i think is that Since the RHS new pressure is Patm. - pgh and the LHS pressure is Patm+pgh. Thus the Increase is equal to RHS-LHS so you get 2pgh.
im a bit late.. but i dont get that... why did u take Patm on the LHS???
i just thought since the difference in the levels of liquid in the arms is taken as 'h' in hpg... when one side goes down by h the other side increases by h... so the difference from the level on the LHS to the level on the RHS side is 2h. ???
Post by: matabd on May 18, 2010, 04:21:57 pm
im a bit late.. but i dont get that... why did u take Patm on the LHS???
i just thought since the difference in the levels of liquid in the arms is taken as 'h' in hpg... when one side goes down by h the other side increases by h... so the difference from the level on the LHS to the level on the RHS side is 2h. ???
Correct. Thats what many of us, thought initially. However maybe u can say that since only the LHS increases by h, the RHS should also increase by h, thus the increase in P should just be Rho-gh. But maybe the formula actually is Delta P (change in P) = rho-g-Delta h (change in h)
Post by: Joseph_COOL on May 18, 2010, 04:26:41 pm
i missed the negative in 10^-4 LOL
Post by: matabd on May 18, 2010, 04:29:54 pm
Good Luck to everyone
Post by: Joseph_COOL on May 18, 2010, 05:12:35 pm
can anyone explain Q36 in June 07??
Post by: Joseph_COOL on May 18, 2010, 05:38:14 pm
Post by: Joseph_COOL on May 18, 2010, 06:07:43 pm
Really need the explanation PLZZZ ???
Post by: 247sports on May 18, 2010, 06:43:18 pm
PLZ someone explain Q36 June 07 and Q25 Nov 07
Really need the explanation PLZZZ ???
find the total current: to find dat I=V/R
total voltage n total current
total resistance = 6
total voltae = 3
so....3/6= 2(total I)
LOSS VOLTAGE = Ir
0.5x2
so the votage delivrd is 2 n power will b VxI so 2x0.5 = 1
this is for m/j 07
tried my best explain hope it helps
Post by: Joseph_COOL on May 18, 2010, 09:44:34 pm
u did ur best and it was more than enough :D
got the idea :D :D
Post by: Allyza1n on May 18, 2010, 11:26:14 pm
im very confused in interference
x = lambda * distance/ slit seperation
so;
when do the fringes appear blured?
when does the intensity increase?
when does the distance increase?
what happens if you use a monochromatic source of light?
thanks in advance :)
Post by: shamanking on May 18, 2010, 11:28:58 pm
Post by: ergonomics100 on May 19, 2010, 06:37:20 pm