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

1. (Original post by annierox1863)
rate of change of momentum is m(v-u)/t units are ms-1/s which makes ms-2 so acceleration surely
What about the kg from the mass

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2. (Original post by Its Andy)
It was a typo. You physically couldn't draw the graph as the current was so small.
The current was halved; I'm guessing one of your equations using factors of 10 were off by 3 magnitudes.

Edit: I stand corrected. Funny, I didn't see a typo on my exam.
3. (Original post by Cmog)
Was it steeper gradient with less area under graph, I forgot to adjust my current
My friend and I both think it was a typo on AQA's behalf must have been 300 ohm or 150 kohm
4. (Original post by Cmog)
I got the same as you except for 2

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5. The question about sketching the graph changed the resistance from 150 ohms to 300 kiloohms, which surely means that the initial current is 2000 times less, and the time constant is 2000 times greater, which must mean that the line would be almost straight and barely above the x-axis?

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6. (Original post by Qwerty1996)

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I was fairly confident with them before but this is great!
7. (Original post by cudders96)
Anyone else notice on the current graph question that the first resistance was 150Ω, but the second was 300KΩ? Think it was probably a typo on AQA's behalf, because the resulting graph would have to start with initial current 2000x lower than the original graph.
I thought exactly the same thing, I definitely messed that question up.
8. What kind of points were people making on the last 6 marker?
9. Bloody hell. Goodbye Firm choice
10. got that!
(Original post by king cobra)
Did people get 1.4 for the height ?

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11. The last multiple choice question, did people put allows current to go to low resistivity sheath or structural reinforcement
12. Here's my answers to the objective test:

13. (Original post by annierox1863)
rate of change of momentum is m(v-u)/t units are ms-1/s which makes ms-2 so acceleration surely
Don't think so
Coz m(v-u)/t the unit will be kgms-2 which is not equivalent to acceleration
14. Exactly what I thought and wrote!

(Original post by Ruyshi)
Surely the ring has no effect on damping... It was placed in such a way that no extra surface area was provided to the cone.. so no effect on air resistance..
time period is no different, so velocity is no difference and so again air resistance does not change..
15. (Original post by annierox1863)
rate of change of momentum is m(v-u)/t units are ms-1/s which makes ms-2 so acceleration surely
You've missed off the Kg unit, Kgms-2 = N
16. (Original post by Cmog)
For the ring/cone pendulum did anyone put that it has no impact upon the damping?
Because damping is the work done by external forces isn't it? and there is no mention of mass in the velocity/acceleration/displacement/time period equations for a pendulum??
That's exactly what I put, I wasn't sure if it was right or wrong but all I knew why that simple pendulums only work with small amplitudes,
17. (Original post by Willow1.21)
I thought exactly the same thing, I definitely messed that question up.
If they've made a typo that impacts it that much, they may even scrap those marks
18. So we're all agreed there was a typo on the 3 mark graph sketching question? No way they meant to make the resistance 2000 times larger, making it impossible to draw a graph. Do we think the question will be voided completely and the exam be made /73?
19. (Original post by Hexaneandheels)
Exactly what I thought and wrote!
Ahh, good to see I'm not alone
20. (Original post by cudders96)
Anyone else notice on the current graph question that the first resistance was 150Ω, but the second was 300KΩ? Think it was probably a typo on AQA's behalf, because the resulting graph would have to start with initial current 2000x lower than the original graph.
Yes I did. If so that is poor on their behalf

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