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

What r u guys doing for optional unit.
I do 5D turning points

Posted from TSR Mobile

Hi can someone tell me if these graphs and the statements I've made at the right hand side are correct. Also do I need to know anymore graphs?

So;

For the velocity graph, the gradient is negative from a maximum when the displacement is to the right of the equilibrium as its trying to accelerate backwards towards the normal.

The gradients are different as velocity always opposes displacement?

And for acceleration its opposite as acceleration is always toward the equilibrium position so as its displaces +ve to the right its acceleration is towards the left -ve.

Sorry this is a bit muddled, but if someone could tell me if I'm correct or just make it a little easier that would be great thanks )))


Posted from TSR Mobile

Me too!! How you finding it? All the papers where standard questions from the old slyabus until last year so now I'm kinda worried :///


Posted from TSR Mobile

For SHM if you have been given displacement: x(t)=Acos(omega.t) for eg. You can easily derive the trig waveforms for velocity and acceleration just by taking the time derivative.
dx/dt=v(t)=-AomegaSin(omega.t)
d^2x/dt^2 = a(t)=-A(omega)^2Cos(omega.t).
I find this easier when asked to draw curves for velocity/displacement/acceleration. You can go backwards through the anti-derivative.

Also this works for emf:
Nphi(t)=BANSin(omega.t) then
E=-dNphi(t)/dt which is just -BAN(omega)Cos(omega.t)

I find it easier to think of it mathematically, however, if you don't take maths then this will be useless

Hi yeah I do understand this I just struggle applying it this way, just the way I am


Posted from TSR Mobile

"Newton's third law states that when an object exerts a force on another object, there is an equal but opposite force exerted on the first object by the second".
If there are equal but opposite forces exerted on the bodies during interactions then the forces would cancel each other out and nothing would ever change their momentum! How true is that?
This question is from OCR but i cannot seem to find it now as my teacher gave it to us last year after finishing the course.


Posted from TSR Mobile

"Newton's third law states that when an object exerts a force on another object, there is an equal but opposite force exerted on the first object by the second".
If there are equal but opposite forces exerted on the bodies during interactions then the forces would cancel each other out and nothing would ever change their momentum! How true is that?
This question is from OCR but i cannot seem to find it now as my teacher gave it to us last year after finishing the course.


Posted from TSR Mobile

Object would come to rest if they were completely inelastic
In really life all objects are elestic.

Think about rebounds

Posted from TSR Mobile

Ah thanks a lot ☺ it'd be great if you could upload a picture, should you find it, because I don't think my teacher showed us.

Just posted it then thought I should probably have quoted you in! It's on the page before this post

Just posted it then thought I should probably have quoted you in! It's on the page before this post

This is a very common mistake - the forces are acting on different bodies - force one acts on body two, force two acts on body one. If the forces are equal and opposite on the same body, then yes, they do cancel out, but otherwise they cause changes

As requested earlier, photos of the multiple choice sheet:

(hopefully these have actually all uploaded successfully, the internet is not being cooperative)
So the real thing will obviously not be a bad photocopy, and the name section was added by our teacher, but this is how you fill in your answers for the multiple choice. A lot of people don't seem to have been made aware that this exists so make sure you leave enough time to fill it in in the exam!

There isn't a section for us to write details in, but the top right ("For office use only") appears to have our centre number and some random persons candidate number printed on it so I'm not sure if this is filled in by the college or something like that beforehand, or if the papers are just attached to the rest.