x Turn on thread page Beta
 You are Here: Home >< Physics

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

1. RATE of change of momentum is a force which was weight it really isn't too hard
2. (Original post by joesterman)
What did you guys get on the written for the number of degrees the lead ball turned through? I got 131 or something similar?
Same, and I know two others who got this
3. (Original post by mrno1324)
Do you remember how the questions was worded?
No sorry :c.
4. (Original post by Mehrdad jafari)
The rate of change of momentum is acceleration. A body cannot accelerate if it's momentum doesn't change

Posted from TSR Mobile
No, force = rate of change momentum look up newton's 2nd law

if you don't believe newton Force = Mass x Acceleration = Kg x Ms-2 = N!!!!!!

by saying unit of force = unit of acceleration you're saying that Mass has no unit, which is totally wrong
5. Also for the electron question why are people saying the number halves? To 2.2x10 to the something
6. (Original post by Mehrdad jafari)
The rate of change of momentum is acceleration. A body cannot accelerate if it's momentum doesn't change

Posted from TSR Mobile
But the unit of rate of change of momentum is Newtons as it equals Force. So how can it be acceleration. I do not understand
7. (Original post by M1llward)
The Electric field strength should have been negative as the charge was negative. -1560 Vm^-1.

I got this wrong.

Also any clues on the damping question? I wrote there would be more damping without the ring as the total energy given to the system with the ring will be greater as GPE=mgh. The work done against air resistance is the same as time period is not affected - because the pendulum system has more energy with the ring it will take longer for the initial energy to be lost through doing work against air resistance. Thus the amplitude will decrease at a slower rate.
Your answer makes sense assuming the initial displacement of both was the same and it wasn't pushed by a force(to its initial displacement). I can't remember if it mentioned this.
8. (Original post by king cobra)
Did people get 1.4 for the height ?

Posted from TSR Mobile
yes

(Original post by Ruyshi)
Surely the ring has no effect on damping... It was placed in such a way that no extra surface area was provided to the cone.. so no effect on air resistance..
time period is no different, so velocity is no difference and so again air resistance does not change..
I said what you did but I realise its wrong

light damping has no effect on the time period because Amplitude is not related to time period, but with damping the amplitude generally increases

heavier damping should be with the ring on i think
9. For the coil with a power supply and ammeter, which way should the needle have initially gone? And which way should it have gone in the next part?
I explained using lens's law and faradays law, did anyone else do this?
10. (Original post by Greg213)
Yep
Don't you get 4mJ from the battery and then minus 2mj to get the energy used up which is 2. So B couldn't havw been incorrect.
11. (Original post by Alexie56)
Only the discharge was using a different resistor, i think they wanted you to assume they start at the same current. Then they just increased resistance. I'm not too sure but I don't think they would've made a typo.
I don't quite understand: There is nothing to assume here, everything can be calculated. The current in a circuit is affected by the load resistance and the electrical energy supplied by the battery. In this situation, electrical energy, i.e. voltage, supplied is the same, but the load resistance is higher. Therefore, this causes the current to decreases as there is more opposition to it in the circuit.
12. First question 10000% was weight, by laws of dimensional analysis 😋
13. What was the capacitance curve supposed to be? I didn't even register that one of them was supposedly 'k' ohms
14. (Original post by TheRAG)
So do you think B is correct then?
Whichever one had the largest area. I remember it being a square with side length 0.5. If that one was option B then yes, B is correct.
15. (Original post by NEWT0N)
Yes, and KE is proportional to v^2 since the factor of 0.5m is constant since both are electrons and therefore have the same mass m.

Kinetic energy of x is twice that of y, hence by what I just said. Hence .

Now, the field exerts a force of F=BQv on a charge Q moving at right angles to the field with velocity v. BQ is the same for both electrons for obvious reasons, so F is proportional to v. Therefore, which is the same as . (option B I think)
I got that too! And i think it was option C but it doesnt matter
16. (Original post by NEWT0N)
Yes, and KE is proportional to v^2 since the factor of 0.5m is constant since both are electrons and therefore have the same mass m.

Kinetic energy of x is twice that of y, hence by what I just said. Hence .

Now, the field exerts a force of F=BQv on a charge Q moving at right angles to the field with velocity v. BQ is the same for both electrons for obvious reasons, so F is proportional to v. Therefore, which is the same as . (option B I think)
Yeah, might be the one for that question

Posted from TSR Mobile
17. (Original post by TheRAG)
For Coulombs law, would I get any marks for quoting the formula and saying what each symbol meant?
Yeah they've accepted that in past papers so should be fine

Posted from TSR Mobile

18. My multi choice, might not have done well though
19. (Original post by Humbers)
No, force = rate of change momentum look up newton's 2nd law

if you don't believe newton Force = Mass x Acceleration = Kg x Ms-2 = N!!!!!!

by saying unit of force = unit of acceleration you're saying that Mass has no unit, which is totally wrong
So the answer should have been weight?
20. (Original post by Disney0702)
But the unit of rate of change of momentum is Newtons as it equals Force. So how can it be acceleration. I do not understand

It isn't acceleration the guy you quoted got it wrong. You are right rate of change of momentum is force which has the unit Newtons

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: February 22, 2016
Today on TSR

My friend is really wealthy

...and I'm jealous

I have imposter syndrome at Cambridge

Poll
Useful resources

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE