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

1. (Original post by Dante991)
I'm looking for someone to show me how to do them too, absoulte killer paper
I hope ours is much more straight forward but I doubt it considering how my exam's have gone so far this year, I've just lost all motivation to revise -_-
2. I'm going to fail ...
3. (Original post by C-king)
BUMP
4. (Original post by DanielWall96)
I'll try help link me the questions
http://filestore.aqa.org.uk/subjects...1-QP-JUN14.PDF

19, 20 & 21 please, thanks.
5. (Original post by samlyon)

Can anyone explain 2b please, how do you know what the phase difference is from the frequency?
Anyone? I'm just confusing myself
6. so each charge is providing half the potential
25/2 = 12.5

The potential from P is doubled as the distance is halved so = 25
The potential from Q is decreased by 1/1.5 so becomes 8.333333333
25 + 8.3333333= 33.3

C
7. (Original post by QueNNch)
Hey guys does anyone know how to calculate the time period for this:
January 2011

The correct answer is B but my calculations can never get that answer.
Apparently we are supposed to use ω2r = 9.81

Thanks
If the object is to appear weightless, then the centripetal force needs to be equal to the weight, so that the resultant force is zero. Therefore mg = mw2r. The masses cancel each other out, so that gives you w2r = 9.81. Then substitute 2pi/T for w and rearrange to get the answer.
8. Thanks a lot JaySP C-king DanielWall96 Klaxoii AR_95 jh52
You all were really helpful. Thanks a lot!
It all makes sense now

Rep'd
9. (Original post by JaySP)
ahh thanks, I was doing this but thought it was too much working for one mark, these questions are too deceptive
10. (Original post by C-king)
ahh thanks, I was doing this but thought it was too much working for one mark, these questions are too deceptive
Don't ever think that with MC. It can vary from plugging into an equation without doing any work, to 3 or 4 step questions
11. Hi
Does anyone have any ideas about what the 6 marker could be on?
12. (Original post by C-king)
ahh thanks, I was doing this but thought it was too much working for one mark, these questions are too deceptive
Thanks for this, I started off correctly but didnt know you divided the 2 equations
13. Attachment 425043425047Attachment 425043425047425000 Sorry some are clearer than others
Attached Images

14. (Original post by C-king)
Attachment 424989
Can someone pls help me on this have no clue
using E=0.5CV^2 derive two equations (leaving units in microfarads) so you get

3200 = CVsquared

800 = C(V-2)squared

you got two simultaneous divide first eqn by V and the sub into 2 hence you get v = 4 and then get C from eqn 1 again (although I would rather stick with plotting each of those 4 answers in the eqn and check by verification)
15. (Original post by C-king)
BUMP
16. (Original post by samlyon)
Anyone? I'm just confusing myself
Think about moving a spring very slowly. You'd barely be affecting the oscillations which is what its getting at with 0.2 Hz.

1.5hz is resonance as its the same as the natural frequency.

As for 10Hz, you must remember those resonance curves, right? Think of what happens to the amplitude as the driver frequency exceeds the natural frequency.

Edit: I didn't pay attention to your question. When in resonance , the driver and the displacement of the oscillation system are 90 degrees out of phase. It's just a fact.
17. Are we allowed Graphics calculators in the physics exams?
18. (Original post by AnneOldman)
Does anyone know any examples of the different types of damping?

Posted from TSR Mobile
Light damping:
person on a swing

Heavy damping:
used in some earthquake proof buildings

Critical damping:
used in suspension systems, i.e shock absorbers

Hopefully this helped.

19. (Original post by JaySP)
Impulse=∆momentum=kgms-1=Ns
Thanks mate is there ever a unit kgms-2

Posted from TSR Mobile
20. Someone give me a question they can't do, multiple choice is my favourite!

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