A-Level Physics 2016/2017 Past Paper Qs Discussion Watch

CJBizzle
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Ask about past paper questions that you aren't sure about, or solve questions for us that aren't sure. Lets get some last minute clarity
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CJBizzle
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(Original post by CJBizzle)
Ask about past paper questions that you aren't sure about, or solve questions for us that aren't sure. Lets get some last minute clarity
To Start off, (7408/1) 15th June 2017 Paper 1, Question 02.2; I cant figure out from the mark scheme how they got to creating the formula to solve for the length l of the string used, any help?
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G.Y
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(Original post by CJBizzle)
To Start off, (7408/1) 15th June 2017 Paper 1, Question 02.2; I cant figure out from the mark scheme how they got to creating the formula to solve for the length l of the string used, any help?
You have to use density to work out the mass per unit lengthName:  F80C457C-D73C-4C06-A7CF-778042F0B4CF.jpg.jpeg
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yesboyyes
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Now I've boiled down the equation to "kl/pi(d/2)^2. By using that equation, I keep getting 12E as the answer, but it should be E. Am I doing something wrong?
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G.Y
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(Original post by yesboyyes)

Now I've boiled down the equation to "kl/pi(d/2)^2. By using that equation, I keep getting 12E as the answer, but it should be E. Am I doing something wrong?
The material is IDENTICAL.

E is a property of a material so it will be the same.
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yesboyyes
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(Original post by G.Y)
The material is IDENTICAL.

E is a property of a material so it will be the same.
god dammit
thanks man
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roxy100
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(Original post by yesboyyes)


Now I've boiled down the equation to "kl/pi(d/2)^2. By using that equation, I keep getting 12E as the answer, but it should be E. Am I doing something wrong?
My guess is that the Young Modulus is a unique property for each material. So because they are made from the same material, the length and diameter doesn't alter the Young Modulus which is why it is E.

A similar thing would be resistivity is a property of a material, so two wires made from the same material would have the same resistivity regardless of length/area
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CJBizzle
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(Original post by G.Y)
You have to use density to work out the mass per unit lengthName:  F80C457C-D73C-4C06-A7CF-778042F0B4CF.jpg.jpeg
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The more i think about it the more i feel im missing something big, i understand the part on the right, but where does the (1/2L)x[SQR](T/u) come from? i'm presuming its related to part 1 but i cant derive it.
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yesboyyes
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(Original post by CJBizzle)
The more i think about it the more i feel im missing something big, i understand the part on the right, but where does the (1/2L)x[SQR](T/u) come from? i'm presuming its related to part 1 but i cant derive it.

Formula booklet mate
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CJBizzle
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(Original post by yesboyyes)

Formula booklet mate
FFS thats why, I'm still on 2010s formulae booklet, nice one pal
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G.Y
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(Original post by CJBizzle)
The more i think about it the more i feel im missing something big, i understand the part on the right, but where does the (1/2L)x[SQR](T/u) come from? i'm presuming its related to part 1 but i cant derive it.
It's given in the formula booklet
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yusyus
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2017 paper 1 AS.
Visible spectrum results from excited electrons moving into the lower level at -3.4 eV

What does it mean moving to a lower level at -3.4?



Gives an example: eg the lowest frequency is due to a transition from the -1.5 eV level to the -3.4 level. L1

Surely lowest frequency is 0.54 to 0.85?
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math24601
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(Original post by yusyus)
2017 paper 1 AS.
Visible spectrum results from excited electrons moving into the lower level at -3.4 eV

What does it mean moving to a lower level at -3.4?



Gives an example: eg the lowest frequency is due to a transition from the -1.5 eV level to the -3.4 level. L1

Surely lowest frequency is 0.54 to 0.85?
Can you please link this question?
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yusyus
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(Original post by math24601)
Can you please link this question?
Q 7.5
http://filestore.aqa.org.uk/sample-p...1-QP-JUN17.PDF

Mark scheme
http://filestore.aqa.org.uk/sample-p...W-MS-JUN17.PDF
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G.Y
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I thought the energy absorbed had to correspond exactly to the energy between energy levels in order for electrons to excite and 13 eV doesn’t correspond to any of those so how come this happens?
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assassinjeev22
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(Original post by G.Y)
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I thought the energy absorbed had to correspond exactly to the energy between energy levels in order for electrons to excite and 13 eV doesn’t correspond to any of those so how come this happens?
The situation you are discribing is with a photon. The photons must have energy = the change in energy of energy levels in order to be absorbed (as E is quantised) otherwise they wont be absorbed (if they have more or less energy than the change in energy of energy levels) .But in this case we see that there are electrons being used as the energy source rather than photons. So by collision and transferring some of their Ke (this Ke that they lose is the energy corresponding between 2 energy levels). And so the 13ev, if they transfer 12.75 the electron can move from ground to lvl 3 and the other colliding electron goes away with a Ke of 0.25. Hope this helps!
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man111111
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(Original post by CJBizzle)
Ask about past paper questions that you aren't sure about, or solve questions for us that aren't sure. Lets get some last minute clarity
https://bit.ly/2JsFnv9
can you please help me with 3.3

i thought refractive index only changes for a material and not for light
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G.Y
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(Original post by man111111)
http://filestore.aqa.org.uk/sample-p...1-QP-JUN17.PDF

can you please help me with 3.3
“Page not found”
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man111111
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(Original post by G.Y)
“Page not found”
try it again
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G.Y
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(Original post by man111111)
https://bit.ly/2JsFnv9
can you please help me with 3.3

i thought refractive index only changes for a material and not for light
Different wavelengths of light will have a different refractive index in a given material. The mark scheme is pretty detailed on this question, it explains it well
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