The Student Room Group
Competition - post a photo you've taken of nature >>
Competition - post a photo you've taken of nature >>
Competition - post a photo you've taken of nature >>

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

Scroll to see replies

Original post by gcsestuff
ImageUploadedByStudent Room1433927351.567904.jpg

For question 8 I keep getting d, it's c


Posted from TSR Mobile


Use E=(1/2)CV^2 for capacitors
also P = ΔW/Δt

then you can derive P = ((1/2)CV2)/Δt
so CodeCogsEqn.gif=3.5x106W=4.5MW
Original post by AR_95
I was a few weeks ago. Oddly, the closer I get to the exam, and more work I do, the less prepared I feel


I 100% feel the same! I've learnt more in these couple of weeks but now I feel like I don't know enough


Posted from TSR Mobile
ImageUploadedByStudent Room1433942090.728568.jpg

Is this the reasons why things move quicker with a smaller radius? Also why does a satellite need to move quicker to stop it falling into the earth?


Posted from TSR Mobile
Reply 3323
Avatar for bwr19
bwr19
2
How is the answer to this C and not B? Surely

T=2πl2gT = 2\pi\sqrt{\frac{l}{2g}}

so

2T=2πlg\sqrt{2}T = 2\pi\sqrt{\frac{l}{g}}


????Capture.PNG
Original post by gcsestuff
ImageUploadedByStudent Room1433942090.728568.jpg

Is this the reasons why things move quicker with a smaller radius? Also why does a satellite need to move quicker to stop it falling into the earth?


Posted from TSR Mobile


cuz ksp
Original post by bwr19
How is the answer to this C and not B? Surely

T=2πl2gT = 2\pi\sqrt{\frac{l}{2g}}

so

2T=2πlg\sqrt{2}T = 2\pi\sqrt{\frac{l}{g}}


????Capture.PNG


ah dude thats not how it works. This isnt like maths where you resolve the equation. Its more like if the right hand side of the equation changes by a factor of

1/(root2) then the other side will also go down by 1/(root2)
Original post by Kennethm
ah dude thats not how it works. This isnt like maths where you resolve the equation. Its more like if the right hand side of the equation changes by a factor of

1/(root2) then the other side will also go down by 1/(root2)


Good spot.

I made the same mistake...
Reply 3327
Avatar for bwr19
bwr19
2
Original post by Kennethm
ah dude thats not how it works. This isnt like maths where you resolve the equation. Its more like if the right hand side of the equation changes by a factor of

1/(root2) then the other side will also go down by 1/(root2)


Haha I've realised this now after making the same mistake on a similar question. Thanks for the help.
Reply 3328
Avatar for CD223
CD223
OP
10
Original post by bwr19
Haha I've realised this now after making the same mistake on a similar question. Thanks for the help.


Just did some workings :smile:

ImageUploadedByStudent Room1433942799.701302.jpg


Posted from TSR Mobile
ImageUploadedByStudent Room1433942755.476590.jpg

Am I right in thinking that if all the charges where positive they would cancel each other out and the potential would become zero


Posted from TSR Mobile
image.jpg
Original post by michaelotty
Use E=(1/2)CV^2 for capacitors
also P = ΔW/Δt

then you can derive P = ((1/2)CV2)/Δt
so CodeCogsEqn.gif=3.5x106W=4.5MW
Original post by Sbarron
image.jpg



You beat me to it!
Original post by gcsestuff
ImageUploadedByStudent Room1433942755.476590.jpg

Am I right in thinking that if all the charges where positive they would cancel each other out and the potential would become zero


Posted from TSR Mobile


No, potential is a scalar sum. If you had 2 negative charges and 2 positive charges opposite each other they would cancel out. In this instance, you have to use Pythagoras to get the distance to the centre. You know the opposite charges on the diagonal edges cancel, so therefore you just have the 2 positive charges to deal with. Find out R and sub this in to the potential equation (V=Q/kr)
Original post by CD223
Just did some workings :smile:

ImageUploadedByStudent Room1433942799.701302.jpg


Posted from TSR Mobile

CD223 has just out played me :frown:
image.jpg

Just found this if it helps? My workings out have my own little codes going on as I don't do maths lol
Original post by gcsestuff
ImageUploadedByStudent Room1433942755.476590.jpg

Am I right in thinking that if all the charges where positive they would cancel each other out and the potential would become zero


Posted from TSR Mobile
Reply 3335
Avatar for CD223
CD223
OP
10
Original post by Kennethm
CD223 has just out played me :frown:


Lol! Not outplayed dw :wink:
image.jpg
Original post by EHR223
No, potential is a scalar sum. If you had 2 negative charges and 2 positive charges opposite each other they would cancel out. In this instance, you have to use Pythagoras to get the distance to the centre. You know the opposite charges on the diagonal edges cancel, so therefore you just have the 2 positive charges to deal with. Find out R and sub this in to the potential equation (V=Q/kr)


Yep
Original post by palaseum9
Something like this?



Are you sure it's right to say the viol is parallel?? To me it is perpendicular but in the SAME PLANE
Oh I see what you mean parallel as in the coil as a whole structure... I would still be tempted just to say when the coil is in the same plane instead but what do I know lol
Hi, does anybody know how to solve this?

Quick Reply

Related discussions

Latest

Trending

Trending

Articles for you