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

1. Stuck with these two..

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2. Consider earth as a point mass, the distance (r) is the radius of the earth R + the 3R, so total distance is 4R. So V=GM/4R, and the R's cancel when equating it to V=GM/R on the Earth's surface.
3. (Original post by AR_95)

if this could be explained again
for mass m, E = 1/2 mv^2 so v = root (2E / m)

mass of daughter nucleus = (M - m)

momentum before = momentum after
0 = m * root (2E / m) - (M - m) * v
m * root (2E / m) = (M-m)v
root (2Em) = (M-m)v
v = [root (2Em)] / (M-m)
4. (Original post by AR_95)
is this a question?
Nah it was an answer, I just forgot to quote.
5. Can someone please explain a magnet falling into a coil or give me a link?

Thanks
6. (Original post by frankiejayx)
I dont understand how the potential at a point between two positive charges can be zero? Do you not use scalar addition in which case the resultant could never be zero??
It's scalar addition if two opposite, but equal charges are present, their potentials sum to zero

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7. (Original post by mrno1324)
It's asking for direction of the electrostatic force though, not "applied" force.
there is no applied force.

Kinetic energy of electron reduces and it gains potential energy.

But what I don't get is since plates are

100V - 70V

it is going from higher potential to a lower potential ... so it would lose potential energy .. but however the work against force also makes sense.

Not sure what to make if it
8. I've lost all confidence for this exam after that horrific chemistry exam!
9. (Original post by CD223)
It's scalar addition if two opposite, but equal charges are present, their potentials sum to zero

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Okay thanks, on a question it had two positives with a point X of 0 potential in between, but im guessing one of the charges were meant to be negative!
10. Can somebody take a look at this please!

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11. (Original post by Bealzibub)
there is no applied force.

Kinetic energy of electron reduces and it gains potential energy.

But what I don't get is since plates are

100V - 70V

it is going from higher potential to a lower potential ... so it would lose potential energy .. but however the work against force also makes sense.

Not sure what to make if it
Really need some kind of online resource that can illustrate this sort of stuff. The books don't help much at all.
12. (Original post by Lau14)
F324? Yeah same :/
No AQA for me. was a terrible paper. pretty sure about 8 marks of it were not even on the specification...
13. Can someone list what happens when you travel along field lines, along lines of equal potential, etc for electric and magnetic fields?
I don't really get the work done thing/ force on particle in these situations
14. Hi, could someone please explain these questions? Sorry for the amount!Attachment 422229Attachment 422229422231Attachment 422229422231422200
15. Can anyone explain ehat they mean by E in the june 14 six marker
I get the rest but dont get wat theyre referring to by E
http://filestore.aqa.org.uk/subjects...W-MS-JUN14.PDF
http://filestore.aqa.org.uk/subjects...2-QP-JUN14.PDF
16. Is anyone else revising from the CGP guide rather than the nelson thornes book
17. (Original post by Klaxoii)
Can somebody take a look at this please!

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Hope this will get you the right answer

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18. could someone help me understand why gravitational/electric field strength is vector please?
19. Thanks

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20. Attachment 424703424711424700[attach]4.2470342471142474e+23[/attach]Attachment 424703424711Could someone help me out with these please! Sorry there are so many but any help would be greatly appreciated
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