# AQA Physics PHYA4 - 20th June 2016 [Exam Discussion Thread]Watch

2 years ago
#741
(Original post by Charlie1523)
Can someone help me with this question: Question 9 http://filestore.aqa.org.uk/subjects...1-QP-JAN13.PDF thanks
There is a formula for it. x(n+1) = yn, where x is the pendulum with the shorter time period. In this case:
1.90(n+1) = 1.95n
1.90n + 1.90 = 1.95n
0.05n = 1.90 therefore n = 1.9÷0.05 = 38 oscillations.
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2 years ago
#742
(Original post by Yo12345)
Attachment 553000

Just to clarify. Is no work done when a charge moves perpendicular to a uniform electric field? Is work only done when the charge moves parallel to the field lines?

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2 years ago
#743
(Original post by spanisholive)
There is a formula for it. x(n+1) = yn, where x is the pendulum with the shorter time period. In this case:
1.90(n+1) = 1.95n
1.90n + 1.90 = 1.95n
0.05n = 1.90 therefore n = 1.9÷0.05 = 38 oscillations.
Thanks Does this formula apply for all situations regardless of the time difference between oscillations?
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2 years ago
#744
(Original post by SirRaza97)
Cheers i understand it now thanks.
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2 years ago
#745
(Original post by alevelstresss)
Gravitational field strength is a vector quantity, given by g = GM/r2

Make the two field strengths equal and find the distance:

let x be the distance of equal field strength from M

GM/x2 = 4GM/(d-x)2
4x2 = (d-x)2
4x2 = d2 -2xd +x2
3x2 + 2xd - d2 = 0
d = 1/3, d = -1 (using quadratic formula)

but d > 0, so d = 1/3 only

the distance is d/3 from the planet of mass M

so the answer is y/d = 1/3
Cheers i understand it now thanks.
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2 years ago
#746
(Original post by Charlie1523)
Thanks Does this formula apply for all situations regardless of the time difference between oscillations?
Yep I believe so
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2 years ago
#747
(Original post by spanisholive)
Sure, here it is Question 6 btw
I've asked a friend and we both got the same answer (from P to Q). I dont know what the hell this Mark shcme is saying. The field doesnt even go in that direction
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2 years ago
#748
Does anyone know why last year's grade boundaries were so low? 59/75 was 120/120 UMS.
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2 years ago
#749
(Original post by Yo12345)

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moving perpendicular to a field uses no work as its an equipotential line however moving in any other direction uses work i believe.
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2 years ago
#750
(Original post by veldt127)
Does anyone know why last year's grade boundaries were so low? 59/75 was 120/120 UMS.
I really have no idea. Maybe a lot of students didnt do as well. Hopoefully it's like that for us!!!
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2 years ago
#751
(Original post by SirRaza97)
I really have no idea. Maybe a lot of students didnt do as well. Hopoefully it's like that for us!!!
I hope so, we have to do Medical as our option unit, my only hope for an A* is a strong mark in Unit 4
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2 years ago
#752
Is everyone doing Section B first?
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2 years ago
#753
(Original post by veldt127)
Does anyone know why last year's grade boundaries were so low? 59/75 was 120/120 UMS.
There was a printing error in one of the questions; the capacitor one.
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2 years ago
#754
(Original post by SirRaza97)
I've asked a friend and we both got the same answer (from P to Q). I dont know what the hell this Mark shcme is saying. The field doesnt even go in that direction
Yeah I don't really understand it either Is it P to Q or Q to P? I thought it would've been Q to P using the left hand rule?
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2 years ago
#755
(Original post by particlestudent)
Is everyone doing Section B first?
yup
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2 years ago
#756
Are we meant to round numbers for further calculations? I tend to use exact values but often get a different answer from the mark scheme but I just assumed it's better to keep the accuracy.

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2 years ago
#757
(Original post by Nikulp68)
There was a printing error in one of the questions; the capacitor one.
That makes sense, damn, looks like an A* might be out of reach. Thanks for explaining +1
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2 years ago
#758
(Original post by spanisholive)
Yeah I don't really understand it either Is it P to Q or Q to P? I thought it would've been Q to P using the left hand rule?
Sorry Q to P is right.
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2 years ago
#759
(Original post by alevelstresss)
yup
I honestly don't know which one to do first...
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2 years ago
#760
Typically I will take a look at Section B and see how hard it looks. Lol.
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