Year 12s: what will be the first way you research your future options? >>

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

Scroll to see replies

We talk about uniform magnetic fields in our spec so the flux density remains the same at different distances.

Radius = mv / BQ

So the radius is proportional to the velocity. B remains the same at different radii

Yeah I though so, just wanted to check, this caught me out on the june 12 paper question about the LHC.

You have any idea about how gravitational potentials caused by a mass is affected by another mass being added to a system?

Do potentials add or subtract....Im sure Ive seen an MC question like this regarding electric potential

Reply 661

MarcusAMM

http://filestore.aqa.org.uk/subjects/AQA-PHYA4-2-QP-JUN12.PDF
http://filestore.aqa.org.uk/subjects/AQA-PHYA4-W-MS-JUN12.PDF

Question 1 b) (ii) and (iii)

surely the units here when multiplying kg/s and m/s they would just give you (N) rather than momentum per second (Ns) and they later do for part (iii) where you can see 1.68 is now in newtons?

something small but the units don't make sense to me, any help appreciated

Reply 662

Lychee628

Original post by SirRaza97

First think which one is more positve and which is more negative relative to each other. Then it's a basic + to - radial ellectric field.

The right one is more positve but idk how to sketch it?

Reply 663

boyyo

Can someone give me the perfect AQA definition of Gravitaional potential energy please

Reply 664

duncant

No problem

Original post by boyyo

Where you said to think about gravitational potential, A says potential energy, so how did you know to use gravitational potential?

by gravitational potential, I mean gravitational potential energy. You are probably wondering why I didnt use Ep=GMm/r, I dont really like that equation. If you use Ep=mgh, when h is higher, Ep is higher. So as you get closer to earth, your Ep falls.

Original post by boyyo

Also even using gravitiational potential, isnt it still inversely proportional to r aswell?

I was on about g=GM/r^2, not g=-change in V/change in r (which is another equation I dont like haha).

Reply 665

duncant

Original post by boyyo

Can someone give me the perfect AQA definition of Gravitaional potential energy please

gravitation potential is the work done per unit mass to move a small test mass from infinity to that point in a gravitational field.

Reply 666

boyyo

Original post by philo-jitsu

yh I remember seeing something like that too. I think they add, but the + and - cancel to make them subtract

Reply 667

boyyo

Original post by duncant

gravitation potential is the work done per unit mass to move a small test mass from infinity to that point in a gravitational field.

Ah ok, what about Gravitational potential energy?

Reply 668

boyyo

Original post by duncant

No problem

by gravitational potential, I mean gravitational potential energy. You are probably wondering why I didnt use Ep=GMm/r, I dont really like that equation. If you use Ep=mgh, when h is higher, Ep is higher. So as you get closer to earth, your Ep falls.

I was on about g=GM/r^2, not g=-change in V/change in r (which is another equation I dont like haha).

lol ok i get you now. Just another quick question, can you use Ep=mgh, when its over large distances?

Reply 669

GigaTrion

does anyone have a list of units we have to know such as 'k' for spring constant or something like that?

Reply 670

duncant

Original post by boyyo

lol ok i get you now. Just another quick question, can you use Ep=mgh, when its over large distances?

nah since g will change over large distances. and sorry didnt read your question, gravitational potential energy is the energy an object possesses due to the fact it is in a gravitation field

Reply 671

justalawyer1998

Original post by philo-jitsu

I may be wrong here but isnt the forces on both vertical sides kind of directed inwards...?

would the coil even rotate if it wasnt already moving, what I mean is the forces direction is perpendicular to the horizontal so how would they even rotate?..

I may be over complicating it

Your first point is right. The forces are inwards and along the same line of action. Hence they cause no torque

Reply 672

boyyo

Original post by duncant

nah since g will change over large distances. and sorry didnt read your question, gravitational potential energy is the energy an object possesses due to the fact it is in a gravitation field

ahh cool, thanks man :smile:

Reply 673

Imtheish

Is anyone having trouble doing past papers in time cause I am. What can I do to improve I know day before the exam. 😅🔫

Reply 674

username2291833

Hey Guys

Any tips on how to manage time in the exam? I.e answer the paper first and get to the multi choice after?
Or is it just try and plough through it all in the time

Cheers

Reply 675

SirRaza97

Original post by Ayaz789

The right one is more positve but idk how to sketch it?

Like this. Sorry its in landscape.

Reply 676

rory58824

Original post by SirRaza97

Like this. Sorry its in landscape.

I thought like charges repel?

How do you do this?

Original post by Nikhilm

Your first point is right. The forces are inwards and along the same line of action. Hence they cause no torque

How are the forces not a couple then? if they are pointing towards one another they are two equal in magnitude forces that oppose one another....isnt that a couple?

Reply 679

alevelstresss

Original post by xMillnsy

How do you do this?

Find the speed at which the water moves

speed is equivalent to a length per second, so speed = volume / area

mass = density x volume

momentum = mass x velocity