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

Reply 3940

Fred Cantoni

2

Any one else get A A A as the first three MC?

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Reply 3941

RThornton

4

Original post by king cobra

What about the angle in degrees ?

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131 ish?

Reply 3942

annierox1863

1

my answers i can remember
forced vibration made by driving force and are in phase, amplitude smaller than at resonance
resonance is at natural frequency and 90 out of phase amplitude large
ring did affect the pendulum THIS IS WRONG THOUGH :-(
RING DOESNT AFFECT DAMPING I DONT THINK
coulombs law: force of two point charges is inversely proportional to the square of distance and proptional to the product of its charges
3300 electric field strength
no. of rotations 0.3 ?
degress angle 2.2
tension 12.34
graph half the current at start then levels out to the same point as other curve
6 mark
Quote three laws, mention centripetal force and acceleration, velocity changes
Not horizontal due to gravitaion force
unit wb (flux linkage) 0.0608 ? not sure
4.48v somthing for emf

Reply 3943

jf1994

15

I put that damping was greater with ring because restoring force was proportial to mg, and energy was Fs so energy was mgs which is dependent on mass, high mass means higher energy lost to resistive forces. No idea if its correct, I was babbling

Reply 3944

RThornton

4

Original post by annierox1863

my answers i can remember
forced vibration made by driving force and are in phase, amplitude smaller than at resonance
resonance is at natural frequency and 90 out of phase amplitude large
ring did affect the pendulum THIS IS WRONG THOUGH :-(
RING DOESNT AFFECT DAMPING I DONT THINK
coulombs law: force of two point charges is inversely proportional to the square of distance and proptional to the product of its charges
3300 electric field strength
no. of rotations 0.3 ?
degress angle 2.2
tension 12.34
graph half the current at start then levels out to the same point as other curve
6 mark
Quote three laws, mention centripetal force and acceleration, velocity changes
Not horizontal due to gravitaion force
unit wb (flux linkage) 0.0608 ? not sure
4.48v somthing for emf

You have the angle in radians there, it asked for degrees

Reply 3945

Absent Agent

21

Original post by king cobra

What did u get ?

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Let me go to a coffee shop so that i can take a picture

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Reply 3946

cudders96

1

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.

Reply 3947

EmiratesCaptain

2

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??

I put no impact, not sure if its right!

Reply 3948

Its Andy

2

That capacitor question annoyed me so much. I was internally raging. I worked out that the current dips 1/400 of a square.

It still annoys me now. Here's a graph of a capacitor discharging, what happens when we times the resistance by 2000?

Now try and draw that on the same axis.
B******s

Reply 3949

Klaxoii

2

First 5 MC I got CAADA but i'm sure the first is wrong

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Reply 3950

Ilovemaths96

13

number of rotations i got 2????

Reply 3951

davidharris96

1

Original post by Fred Cantoni

Any one else get A A A as the first three MC?

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No, D A A
D was the correct answer as Rate of change of momentum is F = (mv-mu)/t
force unit is Newtons

Reply 3952

Fred Cantoni

2

Original post by Klaxoii

First 5 MC I got CAADA but i'm sure the first is wrong

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Think I got AAADD :/

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Reply 3953

michaelotty

1

This http://youtu.be/HV4FNXt1F6Y shows that without ring has heavier damping

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Reply 3954

Kkdhaliwal

1

Bit of an odd paper-personally found MC easier than the written paper...
Waiting for UNNOFICIAL markscheme .... Hopefully should have one by this evening?

Reply 3955

Cmog

2

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.