Physics Paper4

[Sue T]

M/j 2005 5(b)

ur plottin the gradient of th given graph against time it should look like this

[Sue T]

o/n 2005 for question 3b (i) why is work done negative, isnt work dont on the system?

ok so you calculated and its all fine - its not work done on the system - if you think about it the water or now steam would have 2 push against the atmospheric pressure - so its work done by the system - now:
delta U = delta W + delta Q
where U is internal energy, W is work done on the system, and Q is heat given to the system
notice how there aren't any negative signs in the equation
but when you come to calculate the last part, you cantttt take delta W as positive - since its by the system - therefore you put it in as : ''negative work done on the system''  = work done by system
get it?

[Sue T]

M/j 2006 4(c), Q7 (a) and (b)

use ur imagination (though its physix)

[elemis]

Good job Sue T. Keep it up and thanks for helping out our members !

[ruby92]

Thank you  
could you attached the working for the m/j 2004 question?

[Sue T]

thank you Ari Ben Canaan

M/j 2006 4(c), Q7 (a) and (b)

7 a nd b ) cant help with a sorry - wen i asked my teacher he simply said tht i shod no it...
so b) since electrons behave as waves, they get diffracted by the carbon which acts as a diffraction grating. the atoms in the carbons form rows and columns. The spaces between the columns are regularly spaced just like a diffraction grating - this causes the appearance of a central maxima and interference maximas on both sides of it. Then the atoms are also in rows with regular spaces. These give interference maxima above and below the previous central maxima - so you end up with shape 1 in the attachment (very rough sketch)
now there all several jumbled up layers of the atoms just described. so look at the second attachment - you end up with concentric circles as ur diffraction pattern

[Sue T]

Thank you  
could you attached the working for the m/j 2004 question?

[yasser37]

can anyone explain question 5
November 02
parts a and b

how do we put the capacitors and why please
thx

[Sue T]

can anyone explain question 5
November 02
parts a and b

how do we put the capacitors and why please
thx

[thecandydoll]

i have come across certain places that 2*E(kinecticenergy) =  change in potential energy?
howww?

[Sue T]

i have come across certain places that 2*E(kinecticenergy) =  change in potential energy?
howww?

i can only help you if u specify where and what u saw but in general energy is conserved  so ek lost=ep gained

[thecandydoll]

october/n 2008 q5 a

[Sue T]

O/n2006 7b
M/j 2007 Q3 d

so if you increase the frequency, the wavelength decreases.Wavelength affects the number of photons per unit time so a dec in this means a dec in that. intensity remains same. dec in the number of photons per unit time means a derease in the number of photo-electrons per unit time which is the rate of emission.
keep in mind also an inc in frequency means an increase in th max kinetic energy of the photo-electrons but this is not required in this answer

now mj2007 3d - see the more the electric feild strength, the larger th force ryt? and force is directly proportional to acceleration so for part (i) put it as d=o cuz thats the highest value for E. Then part (ii) put it as a description of E. as in go like >> it decreases and then increases -simply . Now wat would be wrong here is putting in a description of the gradient of the graph wen describing the acceleration - because the gradient of that graph is something else - not a quantity proportional 2 acceleration.

[TJ-56]

October\November 2004 Q3 (c) (ii) How is the new amplitude of 4.5 cm calculated?
Thanx in advance

[Sue T]

October\November 2004 Q3 (c) (ii) How is the new amplitude of 4.5 cm calculated?
Thanx in advance

okkkkk sooooo E directly proportional to A²
E ---------> A²
15x10^-3-------->(5x10^-2)²
(80/100)15x10^-3----------->a²

15x10^-3 . a² = (5x10^-2)² . (80/100)15x10^-3

do the math im tired now