OCR Physics A - G484: The Newtonian World - 18/06/12

Hi Guys, thanks to

for uploading the paper.

I've written a mark scheme by being able to see the paper.
Hope it helps, and please tell me if you disagree with anything - It's not all right these are my answers.


1) a) The net force accelerates the object in the direction of the net force
b) i) The change in momentum of a body due to the force
ii) Area under F/T graph is change in momentum
Change in momentum = mv-mu, u = o, so = mv
Mass is known, so v = change in momentum/m
c) i) 708 (something like this)
ii) 0.5kg
iii) The system is not isolated, external forces are acting
This means the momentum will not be conserved in this system


2) a) Motion in which the acceleration is directly proportional to the displacement
from a fixed point, and in the oposite direction
b) i) V = (2(pi)f)A (Whatever this value was)
ii) 1.59 x10^-3
c) i) Resonance - natural frequency = natural frequency
ii) same shape with lower peak


3) a) i) towards the centre of the circle
ii) F acts perpendicular to the motion, so no work done in direction of
motion, so the force doesn't affect the speed
b) i) Tension = mg, F = tension
Time period, measure circumfrence, s=d/t
ii) Straight line through origin
F proportional to V^2, F = kV^2, K = m/r, so m = Fr/v^2
Read point on the line to determine F and V^2, use known radius

4) a) i) The heat required to change the temperature of 1kg of substance by 1K
ii) fusion - heat needed for solid to liquid
vaporisation - heat needed for liquid to gas
b) i) A-B: KE increases as temp increases, PE remains the same
B-C: KE remains constant as temp is same, PE increases and breaks bonds
ii) I said it was higher at liquid that solid (apparently this is wrong)
c) i) 4.86kW (or there abouts)
ii) power used to heat external components - so power used is less than needed


5) a) Gas molecules move in constant random motion at high speed
b) i) temperature is constant
ii) 700 and something I think
iii) More collisions --> More pressure --> More temp (T proportional to P)

6) a) i) Every objects attracts every other object, force prop. mass x mass
and inversley prop. to distance between squared
ii) Force per unit mass
b) i) v = 2(pi)r/T (can't remember figure - r in m and T in s)
ii) 5.36 x10^26 (or there abouts)
c) I did this wrong - apparently it uses t^3 prop. r^2

Anyone have a reasonably confident answer for 5bii ?

Anyone have a reasonably confident answer for 5bii ?

I put that the SHC of liquid is higher, because the gradient of the graph was shallower, meaning the rate of change of temperature was slower. So more energy is required to heat it by a certain amount compared to that of the solid... how is this wrong?

I wrote about specific heat capacity definition by writing the formulae then explaining each symbol because I saw model answer in Philip Allan revision book which is written by an examiner. It commented on the answer saying it is correct way as well. So would somone like to comment on that.

Who feels like revising Physics?