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ALL CIE PHYSICS DOUBTS HERE !!!
Deadly_king:
--- Quote from: $!$RatJumper$!$ on November 13, 2010, 10:52:46 am ---I see :) that makes it a lot clearer now :) so when would we use the equation Change in K.E + Useful work done = Total k.E in overcoming friction + Change in P.E... like for what types of questions?
--- End quote ---
Hmm...........this equation can be altered. You don't need to keep it fixed. It depends according to the question. I always develop my own equation in the exams though you must obey the principle of conservation of enrgy. ;)
It's only used when you need the principle of conservation of energy.
$!$RatJumper$!$:
So isnt energy being conserved in this system of the car?
Deadly_king:
--- Quote from: $!$RatJumper$!$ on November 13, 2010, 11:12:12 am ---So isnt energy being conserved in this system of the car?
--- End quote ---
Not really since you're not told about frictional force. ;)
$!$RatJumper$!$:
i see ok thank you :) Can u help with W09 P11 Q 14, 22, 23, 26, 27, 28
Thank you.. and sorry if its a lot of questions :)
Deadly_king:
--- Quote from: $!$RatJumper$!$ on November 13, 2010, 11:48:01 am ---i see ok thank you :) Can u help with W09 P11 Q 14, 22, 23, 26, 27, 28
Thank you.. and sorry if its a lot of questions :)
--- End quote ---
Nov 09 p11
11. The centre of gravity of an object is defined as the point at which the weight can be considered to act.
Answer is C
14. Initial k.E is given to be E.
Since the angle of projection is 45o, the initial kinetic energy will divide equally to give the final P.E and the final K.E. ;)
So final k.E will be 0.5E
Answer is A.
22. Youngs Modulus is given as Y = TL/Ae where
T : Tension in the string
L : Length of the string
A : Area of cross-section of the string.
e : extension produced.
You're asked to find the % length the string contracts. Hence you need to find the percentage of e/L which is also equal to F/AY. (from equation above)
Hence replace the values given to you to get 20/(pie*(diameter/2)2*2.0 x 1011) x 100
It will come out to be 0.051%.
Hence answer is B
23. You should know this from the elctromagnetic spectrum. ;)
Max wavelength of U.V = 10-13 and c = 330ms-1
Hence c = f(lambda) -----> f = 330/10-13 = 1015 Hz
Answer is B
26. You should use the formula dsin(theta) = n(lambda) where d = 1/N. Since the beam of light is parallel, theta will be 90o. You should also convert the wavelength into millimetres since N is given as 300 lines/mm.
(1/300) x sin 90 = n(450 x 10-6) ----> n = 7.5
Hence there'll be 7.5 lambda above and 7.5 lambda below. This makes 15 lambda. Each lambda will form one maxima. ;)
Answer is D
27. Force = Electric field x charge
Electric field = Force / charge = F/q
Answer is D
28. Equilibrium => Electric force = Weight
Hence QE = mg ----> Q/m = g/E
Electric force is upwards(opposite to the weight). Since it is attracted towards the positive plate, it has to be negatively charged. ;)
Answer is B
Hope it helps :)
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