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# AQA Physics PHYA4 - Thursday 11th June 2015 [Exam Discussion Thread] watch

1. Hi i was wondering if someone could help me on some MC questions? Its questions 2, 21, 22 and 24 from Jan2011
for Q2 i got B but the correct answer is A
for Q21 I got D but the correct answer is B
and i couldn't do 22 or 24
2. (Original post by Mai.H)
Hi i was wondering if someone could help me on some MC questions? Its questions 2, 21, 22 and 24 from Jan2011
for Q2 i got B but the correct answer is A
for Q21 I got D but the correct answer is B
and i couldn't do 22 or 24
Q2. As your answer is double the correct one, you've most likely not converted the diameter - which is what they gave in the question - into the radius

I'm not great with magnetic fields, but 22 I can manage,

Q22. Magnetic flux is BA. B is given in the question, A is the area the wings cover in 10 seconds. As it's going 150m/s, in 10 seconds it's travelled 1500m. The wingspan is 60 so A = 1500 x 60 = 90000. BA = 0.9 or 9 x 10^-1, D.
3. (Original post by Lau14)
Q2. As your answer is double the correct one, you've most likely not converted the diameter - which is what they gave in the question - into the radius

I'm not great with magnetic fields, but 22 I can manage,

Q22. Magnetic flux is BA. B is given in the question, A is the area the wings cover in 10 seconds. As it's going 150m/s, in 10 seconds it's travelled 1500m. The wingspan is 60 so A = 1500 x 60 = 90000. BA = 0.9 or 9 x 10^-1, D.
Thank you so much! Im terrible at magnetic fields! i just can't get my head round it
4. Would anyone mind explaining the difference between Flemmings LHR and RHR?? Can I use the LHR in both situations and get the right answer??
5. (Original post by frankiejayx)
Would anyone mind explaining the difference between Flemmings LHR and RHR?? Can I use the LHR in both situations and get the right answer??
I think you use the RHR when you want to find the direction of the induced emf, as (from lenz law) it acts in the opposite direction to the motion of the conductor

But you use the LHR to find direction of the force on a conductor using conventional current (that's +ve to -ve)

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6. (Original post by EmiratesCaptain)
I think you use the RHR when you want to find the direction of the induced emf, as (from lenz law) it acts in the opposite direction to the motion of the conductor

But you use the LHR to find direction of the force on a conductor using conventional current (that's +ve to -ve)

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Thanks, so in the RHR is the current flow also + to -?
7. (Original post by frankiejayx)
Thanks, so in the RHR is the current flow also + to -?
Yup - fingers all symbolise the same thing - just different orientation! This time it's the current that's induced rather than a force being produced as with the LHR.

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8. (Original post by Mai.H)
Hi i was wondering if someone could help me on some MC questions? Its questions 2, 21, 22 and 24 from Jan2011
for Q2 i got B but the correct answer is A
for Q21 I got D but the correct answer is B
and i couldn't do 22 or 24
Question 2:

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9. (Original post by Mai.H)
Hi i was wondering if someone could help me on some MC questions? Its questions 2, 21, 22 and 24 from Jan2011
for Q2 i got B but the correct answer is A
for Q21 I got D but the correct answer is B
and i couldn't do 22 or 24
Question 21:

Posted from TSR Mobile
10. (Original post by Mai.H)
Hi i was wondering if someone could help me on some MC questions? Its questions 2, 21, 22 and 24 from Jan2011
for Q2 i got B but the correct answer is A
for Q21 I got D but the correct answer is B
and i couldn't do 22 or 24
Question 22:

Posted from TSR Mobile
11. (Original post by Mai.H)
Hi i was wondering if someone could help me on some MC questions? Its questions 2, 21, 22 and 24 from Jan2011
for Q2 i got B but the correct answer is A
for Q21 I got D but the correct answer is B
and i couldn't do 22 or 24
Question 24:

Posted from TSR Mobile
12. Anyone fancy explaining why the Kinetic Energy curve is a parabola and not a bell-shaped curve? I know it's like that in the books etc, I just wanna know why ;p

13. (Original post by CD223)
Anyone fancy explaining why the Kinetic Energy curve is a parabola and not a bell-shaped curve? I know it's like that in the books etc, I just wanna know why ;p

Ek=0.5mv2
Ek∝v2

v=2πf root(A2-x2)
v2=4π2f2(A2-x2)
v2∝-x2

Ek∝-x2

Constants change it's y intercept I think
14. (Original post by 000alex)
Ek=0.5mv2
Ek∝v2

v=2πf root(A2-x2)
v2=4π2f2(A2-x2)
v2∝-x2

Ek∝-x2

Constants change it's y intercept I think
Oh of course thanks!

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15. likely 6 markers to come up this year?
16. (Original post by AR_95)
likely 6 markers to come up this year?
Personally predicting SHM or circular motion. You?

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17. (Original post by AR_95)
likely 6 markers to come up this year?
Highly unlikely to be capacitance as that came up last year. Simple harmonic motion does seem very likely, as they haven't actually ever had a six marker on it yet, but that could be because it always comes up in the EMPA.
18. (Original post by Lau14)
Highly unlikely to be capacitance as that came up last year. Simple harmonic motion does seem very likely, as they haven't actually ever had a six marker on it yet, but that could be because it always comes up in the EMPA.
Well my ISA was on Capacitors this year haha

Wrt SHM, do you mean experiments then?

(Original post by CD223)
Personally predicting SHM or circular motion. You?Posted from TSR Mobile
Not a clue mate, would love Kepplers law if it hasn't come up before
19. (Original post by AR_95)
Well my ISA was on Capacitors this year haha

Wrt SHM, do you mean experiments then?

Not a clue mate, would love Kepplers law if it hasn't come up before
Kepler's third law came up last year as a "proof" question about Satellite orbits. Not to say it won't come up again but who knows.

I think SHM is most likely - even though the EMPA was on it, it could easily be that as it hasn't been asked yet and there's so much theory on it.

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20. (Original post by CD223)
Kepler's third law came up last year as a "proof" question about Satellite orbits. Not to say it won't come up again but who knows.

I think SHM is most likely - even though the EMPA was on it, it could easily be that as it hasn't been asked yet and there's so much theory on it.

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what sort of theory do you think is likely to come up about SHM?

Are we expected to derive the equations in the written paper for SHM

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