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OCR Physics, Forces, Fields and Energy
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you'll know tomorrow
good luck everyone i need to go to bed now
good luck everyone i need to go to bed now
As long as you get the answer right I don't think they will mind what formula you use. If they specify something particular, like certain variables, then its better to use those with the relevant formula.
Past Essay questions from Jan 04 to Jun 07: SHM, MOM, ALPHA, RAD, ALP/RAD, FARA, FUS/FIS/U-MASS, FARA/LENZ
Jan 08 Guess: Thermal Physics.
Past Essay questions from Jan 04 to Jun 07: SHM, MOM, ALPHA, RAD, ALP/RAD, FARA, FUS/FIS/U-MASS, FARA/LENZ
Jan 08 Guess: Thermal Physics.
aa
(edited 12 years ago)
Agreed, its so much easier to use a =-(w^2)x.
aa
(edited 12 years ago)
How did you find it ?
X-ray diffraction was main essay q. pretty easy.
A few questions rly pissed me off.
1. The question about the two spheres, so u had to use F=kq1q2/r^2. But i kept getting wrong value because i kept doing F = 9x10^9 X 2 X 5x10^-9 / whatever r^2 was instead of F = 9x10^9 X 5x10^-9 X 5x10^-9 / whatever r^2. So annoyed i only realised after handed in.
2. The ratio of molecular speed thing for the ideal gases question. I had no idea. My answer came out as 3 something. Probably wrong.
X-ray diffraction was main essay q. pretty easy.
A few questions rly pissed me off.
1. The question about the two spheres, so u had to use F=kq1q2/r^2. But i kept getting wrong value because i kept doing F = 9x10^9 X 2 X 5x10^-9 / whatever r^2 was instead of F = 9x10^9 X 5x10^-9 X 5x10^-9 / whatever r^2. So annoyed i only realised after handed in.
2. The ratio of molecular speed thing for the ideal gases question. I had no idea. My answer came out as 3 something. Probably wrong.
Just posted a thread with the/my answers to all the paper.
Nope havent scanned it yet - just sat down and did the paper
Usual disclaimer - I've just rocketed through the paper and havent checked these.
Q1 Looks like a nice and easy opener if you can read from the graph successfully.
a) Mgh = 0.22 -> h=1.60m (2)
b) Ke increases at a decreasing rate (2)
c) i) KE = 0.11J -> v = 3.96ms-1 (2)
ii) At terminal vel, drag force up = weight down = mg = 0.137N (1)
iii) Energy loss per second = mgh / t = mgv = 0.543W (2)
d) KE before bounce = 0.11J; v before = 3.96 ms-1 down
KE after bouce = 0.8 x 0.11J; vafter = 3.55ms-1 up
Change in v = 7.5 ms-1 (usual ctach about changing direction)
Change in momentum = 0.105 Ns or kg. m s-1 (4) Total 13
Q2 Always a tricky topic for many people
a) Internal energy = sum of random KE and PE for all paerticles in the system
SHC = energy needed to change temp of 1kg of material by 1K (3)
b) H=mcdT = 1.45E5J (3)
c)i) PV=nRt - sub first set of values to get n=2.65mol
sub second set of values to get n=4.11 mol
dn = 1.46 mol -> change in mass = 0.044kg (4)
ii) Energy is prop to T in Kelvin so ratio of speeds = ration of sqr(temps in kelvin)
= sqr(453/293) = 1.24 (3) Total 13
Q3 Straightforward motion in a circle.
a) i) Arrows marking Tension and weight (2)
ii) Resultant force must be horizontal and towards centre of circle (2)
iii) F = m v^2 / r
b)i) Vert T cos theta = mg
Horiz T sin theta = m v^2 /r
so tan theta = v^2 /rg -> tan theta = 0.36 and theta = 19.8 degrees (4)
ii) Theta will stay the same because doesnt depend on m (1) Total 10
Q4 Not too bad - seen most of this before
a) Charge is +ve so lines leave spehere and go towards plates, top and bottom
Lines must meet spehere and plates at 90 degrees. (3)
b) i) E = V / d = 1.25E6 NC-1 (2)
ii) F = EQ = 6.25 E-3N (2)
c) i) F = q1q2/4Pieor^2 -> 0.14 mN (3)
ii) 0.14 mN = 1.37g
Charges repel so must add to scale reading -> 9.58 g (2) Total 12
Q5 Not too bad - but a few might struggle.
a)i) Flemings LH Rule -> Force is vert upwards (1)
ii) F = BIL -> 4.8E-3 N (2)
b) i) T = 20E-3s f = 1/T = 50Hz (2)
ii) Standing wave has an antinode in middle
Acc is prop to amplitude
Amplitude varies so acc is not same (3)
c) i) Resonance (1)
ii) Peak at 50 Hz so mark in units of 25 Hz on scale (1)
ii) Usual sketch of damped resonance curve - lower / broader/ same resonant f. (3)
Total (13)
Q6 Routine at start, gets harder
a) Beta- decay so a neutron becomes a proton.
Z = proton number increases by one 38-39
N = neutron number decreases by one (137-55) 82 ->81 (2)
b) i) Activity = number of nuclei decaying per unit time (1)
ii) lambda = ln2/t1/2 (Dont forget to convert years to seconds) = 7.33E-10 s-1 (2)
c) i) After 15y N = 3.525E15.
A = lambda N = 2.59E6 Bq (2)
ii) N = No exp (-lambda t) Read a pair of values of N and t from graph, sub and calc No
3.525E15 = No exp (-7.33E-10 x 15 x 3.15E7)
No = 4.98E15 (3)
iii) n = No / Na = 8.3E-0 mol
m = nx mm = 8.3E-9 kg = 8.3 ug (2) Total 14)
Q7 Not a lot needed here - but you have to know this reaonably well
a) Need wavelength of order of spacing.
X ray interference (bragg law)
Diagram and Details of path difference and how to calc spacing
Electron (diffraction) interference. eg graphite
How to calc spacing from ring pattern
Lambda = h/ mv (7)
b) Atom dia 1E-10 - 1E-9
Nucleus dia 1E-15 - 1E-14
Wavelengths need to be less than size of obect to produce diffraction pattern.
(4) + (4) QWC
Usual disclaimer - I've just rocketed through the paper and havent checked these.
Q1 Looks like a nice and easy opener if you can read from the graph successfully.
a) Mgh = 0.22 -> h=1.60m (2)
b) Ke increases at a decreasing rate (2)
c) i) KE = 0.11J -> v = 3.96ms-1 (2)
ii) At terminal vel, drag force up = weight down = mg = 0.137N (1)
iii) Energy loss per second = mgh / t = mgv = 0.543W (2)
d) KE before bounce = 0.11J; v before = 3.96 ms-1 down
KE after bouce = 0.8 x 0.11J; vafter = 3.55ms-1 up
Change in v = 7.5 ms-1 (usual ctach about changing direction)
Change in momentum = 0.105 Ns or kg. m s-1 (4) Total 13
Q2 Always a tricky topic for many people
a) Internal energy = sum of random KE and PE for all paerticles in the system
SHC = energy needed to change temp of 1kg of material by 1K (3)
b) H=mcdT = 1.45E5J (3)
c)i) PV=nRt - sub first set of values to get n=2.65mol
sub second set of values to get n=4.11 mol
dn = 1.46 mol -> change in mass = 0.044kg (4)
ii) Energy is prop to T in Kelvin so ratio of speeds = ration of sqr(temps in kelvin)
= sqr(453/293) = 1.24 (3) Total 13
Q3 Straightforward motion in a circle.
a) i) Arrows marking Tension and weight (2)
ii) Resultant force must be horizontal and towards centre of circle (2)
iii) F = m v^2 / r
b)i) Vert T cos theta = mg
Horiz T sin theta = m v^2 /r
so tan theta = v^2 /rg -> tan theta = 0.36 and theta = 19.8 degrees (4)
ii) Theta will stay the same because doesnt depend on m (1) Total 10
Q4 Not too bad - seen most of this before
a) Charge is +ve so lines leave spehere and go towards plates, top and bottom
Lines must meet spehere and plates at 90 degrees. (3)
b) i) E = V / d = 1.25E6 NC-1 (2)
ii) F = EQ = 6.25 E-3N (2)
c) i) F = q1q2/4Pieor^2 -> 0.14 mN (3)
ii) 0.14 mN = 1.37g
Charges repel so must add to scale reading -> 9.58 g (2) Total 12
Q5 Not too bad - but a few might struggle.
a)i) Flemings LH Rule -> Force is vert upwards (1)
ii) F = BIL -> 4.8E-3 N (2)
b) i) T = 20E-3s f = 1/T = 50Hz (2)
ii) Standing wave has an antinode in middle
Acc is prop to amplitude
Amplitude varies so acc is not same (3)
c) i) Resonance (1)
ii) Peak at 50 Hz so mark in units of 25 Hz on scale (1)
ii) Usual sketch of damped resonance curve - lower / broader/ same resonant f. (3)
Total (13)
Q6 Routine at start, gets harder
a) Beta- decay so a neutron becomes a proton.
Z = proton number increases by one 38-39
N = neutron number decreases by one (137-55) 82 ->81 (2)
b) i) Activity = number of nuclei decaying per unit time (1)
ii) lambda = ln2/t1/2 (Dont forget to convert years to seconds) = 7.33E-10 s-1 (2)
c) i) After 15y N = 3.525E15.
A = lambda N = 2.59E6 Bq (2)
ii) N = No exp (-lambda t) Read a pair of values of N and t from graph, sub and calc No
3.525E15 = No exp (-7.33E-10 x 15 x 3.15E7)
No = 4.98E15 (3)
iii) n = No / Na = 8.3E-0 mol
m = nx mm = 8.3E-9 kg = 8.3 ug (2) Total 14)
Q7 Not a lot needed here - but you have to know this reaonably well
a) Need wavelength of order of spacing.
X ray interference (bragg law)
Diagram and Details of path difference and how to calc spacing
Electron (diffraction) interference. eg graphite
How to calc spacing from ring pattern
Lambda = h/ mv (7)
b) Atom dia 1E-10 - 1E-9
Nucleus dia 1E-15 - 1E-14
Wavelengths need to be less than size of obect to produce diffraction pattern.
(4) + (4) QWC
jwilduk
Yeh I liked the X ray question too. I dunno about the ratios, i got 1.6 I'd be interested to see what other people got
i got 1.5.
i thought the paper was a lot easier than it would be, not entirly convinced it went great, but good. did anyone else spend an age learning electromagnectic induction only to have it not come up? they didn't have anyhting on capacitors either. but other than that they wasn't anything too har on there i thought
imaginary_world
i got 1.5.
i thought the paper was a lot easier than it would be, not entirly convinced it went great, but good. did anyone else spend an age learning electromagnectic induction only to have it not come up? they didn't have anyhting on capacitors either. but other than that they wasn't anything too har on there i thought
i thought the paper was a lot easier than it would be, not entirly convinced it went great, but good. did anyone else spend an age learning electromagnectic induction only to have it not come up? they didn't have anyhting on capacitors either. but other than that they wasn't anything too har on there i thought
I got 1.24 although two people I know got 1.55.
My physics teacher told me that I didn't need to revise x-ray diffraction because it wasn't on our syllabus! Fortunately I ignored him, although I would have looked at it more closely had I known. GRRRRR!
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