AQA Physics PHYA4 - 20th June 2016 [Exam Discussion Thread]

ah **** yeah your right i see, i put the negative in brackets will i lose the marks?

Here are my answers to Written, the question parts might not be correct.

Written answers
1ai) 8.26 (will be a range)
ii) 2.6x10^-4

bi)28
ii)5.9x10^4
iii) bottom box ticked

2ai) Derivation
ii) 6.06x10^6 (3SF only)

b) Downward Curve staring at 9.81
Minimum at g=0 at a point slightly offset from halfway closer to Venus
Rises up to 8.87

3a) V=mv/N

b) Derivation


ci) 216
ii) 1.15x10^-19 kgms-1 OR Ns
iii) Anti electron neutrino released also so Beta minus particles have range of Kinetic Energies upon release.

4a) Small amplitude oscillation as only valid for small angular amplitudes.

b) -Set up light string with Bob on the end,
attach top of string to clamp stand boss.
-Measure length from top to centre of Bob.
-Release the Bob so it oscillates with small amplitude.
-Use stop clock to measure time taken for 20 oscillations.
-Divide this by 20 for mean T
-Plot T^2 against L
-Calc Gradient
g=(4pi^2)/gradient
-Repeat procedure

c) -Student value 4x true value
-Time period half so all values for T^2 will be 1/4 the true
-Gradient is 4x lower
-State equation or show that g is inversely proportional to gradient.

5a) Lenz's Law: Direction of induced EMF/current is always in a direction that opposes the change that caused it.
Faraday's Law: Induced EMF is proportional to rate of change of flux linkage.

b) -Change in flux linkage when current flows.
-EMF induced in wheel (or whatever it was called)
-Current induced in the wheel as good conductor.
-Current carrying conductor (wheel) opposes the field due to coil, therefore there is a force against the direction of motion.

c) Wheel not in contact with electromagnet so no wear, but in brake pads there is wear due to friction.

More energy used or less effective or heating.

I think both answers for increased power drain and electrical failure will be valid. Although my view is that it would be unreasonable to use a powered braking system, because if you park your car on a hill your battery will eventually go flat and then your car will have f***Ed off down the hill by the time you come back with your shopping.

what did people say about the B- emission any why the equations wouldnt work? I said that B emission is an electron which isnt a nucleon, which is what the equations represent?

what did people say about the B- emission any why the equations wouldnt work? I said that B emission is an electron which isnt a nucleon, which is what the equations represent?

no wat, 220 was the nuclean number before it decayed by alpha particle thing
so after it was 220-4 = 216

I said (T/(2*pi))^2 on x axis, l on the y axis - which is right, as gradient is g.

You would possibly lose 1 mark for not saying 'evaluate (T/(2*pi))^2.

Not directly related to the question on the paper but doesn't the magnetic braking system only work when the discs are spinning and so wouldn't be used if parking on a hill. I think there would still have to be a mechanical parking brake.

Was the direction from X to Y or Y to X

for RC i got 202 what did everyone else get
and for R i got some big number 10^5 i think

someone confirm if this is right pls i used v=vo e^-t/rc
where v = 0.8vo

45/(-ln(0.8) = RC

because g iversly proportional to t and t is 4 ti,mes smaler

DBBDDDDBBCBACCCDBACAADCBD

Can anyone confirm with me?

Posted from TSR Mobile

After the 6 Marker there was a 3 Mark Question on about Time Period being miscalculated, 3 Marks on Electromagnetic Laws (maybe 4 pretty sure it was 3 though). A 3 marker on Lenz's Law and then finally a 2 Marker on Disadvantages of Electromagnetic Brakes so you have missed:

About 11 Marks.

Do you remember the marks for each?