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AQA A Physics Unit 4 24th Jan 2012

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Can anyone explain how the answer to Q21 on the june 2011 paper A is answer choice C?? I keep getting B!! :mad:
Reply 141
Do you have a copy of the mark scheme or the paper ?
Reply 142
I was just thinking, does anyone have an answer booklet to have a look how its set out? Ive just realised i have no idea if im ticking boxes, filling in circles etc.
Original post by handsome7654
Can anyone explain how the answer to Q21 on the june 2011 paper A is answer choice C?? I keep getting B!! :mad:


I don't know if my method is correct, but I end up with C, so here goes:

Rearrange w = 2pi*f
T = 2pi/w = 2pi*r/v

BQv = (mv^2)/r
BQ = mv/r
r = mv/BQ

Substitute that in:

T = (2pi*mv)/BQv
T = (2pi*m)/BQ

So, T is proportional to m. If Mp<Mq , then Tp<Tq

I hope that makes sense!
Original post by jones_wise
I don't know if my method is correct, but I end up with C, so here goes:

Rearrange w = 2pi*f
T = 2pi/w = 2pi*r/v

BQv = (mv^2)/r
BQ = mv/r
r = mv/BQ

Substitute that in:

T = (2pi*mv)/BQv
T = (2pi*m)/BQ

So, T is proportional to m. If Mp<Mq , then Tp<Tq

I hope that makes sense!


Ohh I see.. That makes sense now.. thankya!! :biggrin:
I kept rearranging it wrong lol I guess I still need to work on my basics. :tongue:
Feel quite prepared for this exam! ...unlike Economics.

Just need to get Electric Potential into my head - what it is and means exactly... it's kind of confusing when there's so many types of potential all denoted V! :tongue:
Reply 146
Original post by Xero Xenith
Feel quite prepared for this exam! ...unlike Economics.

Just need to get Electric Potential into my head - what it is and means exactly... it's kind of confusing when there's so many types of potential all denoted V! :tongue:


When I was learning the definition about this I got slightly confused; it is, as you know, "The work done in bringing a unit positive charge from infinity to a certain point in an electric field". Is it positive because the convention for an electric field is +ve -> -ve so that work must be done against the direction of the field?

It's a pretty minor query I have here but I don't understand why the definition insists the unit charge is positive :tongue:
Original post by areebmazhar
http://www.egsphysics.co.uk/
go to the exams section and scroll down to a-levels.
Our teacher told us the multiple choice questions get continuously recycled through the years and this is very true. Some people in last year who did the past spec papers, on real exam multiple choice, they hads seen nearly half the questions before, so they already had half the marks without any work. That's probably my best tip


Firstly thanks for the tip.


Secondly does anyone know where I can get June 2011 and answers?
Original post by TheRenaissanceMan
Firstly thanks for the tip.


Secondly does anyone know where I can get June 2011 and answers?


Scroll a few pages back, someone posted a link :smile:
Original post by Femto
When I was learning the definition about this I got slightly confused; it is, as you know, &quot;The work done in bringing a unit positive charge from infinity to a certain point in an electric field&quot;. Is it positive because the convention for an electric field is +ve -&gt; -ve so that work must be done against the direction of the field?

It's a pretty minor query I have here but I don't understand why the definition insists the unit charge is positive :tongue:


If I understand what you're saying, yes, I think so. Little explanation in case you're saying something different:

OK, so we have our unit positive charge, and it's being moved into the electric field - being generated by a positive charge (by default).

It's obviously going to be difficult to move a positive charge closer to another positive charge. This is why there's work done in bringing it closer.

A negative charge moving into a "negative field" would have the same work done when you calculate it - the two minus signs cancel - but electric potential is defined around a positive test charge just... yeah, because it needs a definition. :tongue:

(Physics-people, please yell at me if I'm wrong :colondollar:)
Anyone know the requirements to get an A* overall in physics?
Reply 151
Original post by handsome7654
Anyone know the requirements to get an A* overall in physics?


90% ums average in unit 4, 5 and 6
80% overall in all six modules :smile:

Typically by looking at the previous grade boundaries in unit 4 you need roughly above 58 out of 75 raw marks to get an A*

I'm aiming for it too :smile:
Original post by Ark1
90% ums average in unit 4, 5 and 6
80% overall in all six modules :smile:

Typically by looking at the previous grade boundaries in unit 4 you need roughly above 58 out of 75 raw marks to get an A*

I'm aiming for it too :smile:


Someone told me you have to get 90+ in every single A2 module (4, 5 & 6).
Are you sure it is 90 average? :confused:
Reply 153
Original post by handsome7654
Someone told me you have to get 90+ in every single A2 module (4, 5 & 6).
Are you sure it is 90 average? :confused:


Yeah, I'm pretty sure it's 90 UMS average over 4, 5 & 6 :smile:
Original post by handsome7654
Someone told me you have to get 90+ in every single A2 module (4, 5 &amp; 6).


Lies!

Original post by Machoo
Yeah, I'm pretty sure it's 90 UMS average over 4, 5 &amp; 6 :smile:


This is correct. :smile:

Loads of teachers and schools are utterly misinformed. The conditions for A* are a 90% average across all A2 units, and 80% over the whole A-level. The only exception is Maths, where the module choice is so wide that the definition of "A2 unit" has to change slightly to keep it fair.
Reply 155
For instance, you could get 2 100 UMS's and 1 70 UMS paper, and still get an A* overall as your overall average would be 90 :smile:
Reply 156
Original post by Machoo
For instance, you could get 2 100 UMS's and 1 70 UMS paper, and still get an A* overall as your overall average would be 90 :smile:


Thats what I'm planning :tongue: gonna try and get 120 ums for unit 4 and 5 because I'm useless at the EMPA lol hahaa
Reply 157
I'm absolutely dreading this exam :'(
Original post by Machoo
Yeah, I'm pretty sure it's 90 UMS average over 4, 5 & 6 :smile:


Thankyouu!! Now I have more of a chance of getting an A* lol.. :biggrin:
Original post by Xero Xenith
Lies!



This is correct. :smile:

Loads of teachers and schools are utterly misinformed. The conditions for A* are a 90% average across all A2 units, and 80% over the whole A-level. The only exception is Maths, where the module choice is so wide that the definition of "A2 unit" has to change slightly to keep it fair.


Lol I guess my teacher was wrong too!! :tongue:

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