AQA Physics A - PHYA4 (11/06/12) - Exam thread

What are the values you're getting from each equation?
I got 1.866...x10^-36 for the gravitational force between two masses and 2.3019 for the electrostatic force between them which gives me 1.2336x10^36.

Q.5

w=v/r

Guessing you forgot to half the diameter.

Q.15
2/r^ = 8/(60-r^2) Use ratios but make sure you square the distance.
Square root...

Therefore root 2 /r^2 = 2root2/ (60-r^2)
(root2)(120) - (root2)r^2 = 2(root)2r^2

Rearrange u get r =40mm


Q.16

E is NC^-1 AND Vm^-1

Force x distance = Work done = Nm
therefore Force = work done /distance = Jm^-1

Therefore Jm^-1C^-1 can be used..

1/It =1/Q therefore C^-1 = A^-1s^-1

Sub in therefore JA^-1C^-1m^-1 can be used

C just subs the Newtons back in for Jm^-1

Therefore the answer is D.

For the 6 marker, definitely not anything to do with electricity or the magnetism stuff. I reckon it will be conservation of momentum or some gravity stuff

My mark scheme for that paper says B haha..

I reckon it'll be on resonance

what do you think the main points to include are:


anything else? im not too confident on resonance

can someone help with question 12. The answer is A, but i thought it was B?
http://www.freeexampapers.com/get_past_papers.php?l=Past_Papers%2FA+Level%2FPhysics%2FAQA%2FPhysics+A%2F2005+Jun%2FAQA-PA04A-W-QP-JUN05.pdf

http://store.aqa.org.uk/qual/gce/pdf/AQA-PHYA4-2-W-QP-JUN11.PDF

For question 4c, I don't think you need to know this but would the beam of electrons just be deflected up or would they start to move in a circular path upwards?

Do particles take a parabolic path in electric fields? If so why?

http://store.aqa.org.uk/qual/gce/pdf/AQA-PHYA4-2-W-QP-JUN11.PDF

For question 4c, I don't think you need to know this but would the beam of electrons just be deflected up or would they start to move in a circular path upwards?

yes, because the electrons experience a force which is contiunously in one direction, so they will curve off and exit the other side and continue in a straight path

I keep getting something x 10^-9!....please could you tell me the numbers you have used in each equation?

For the gravitational force:

( (6.67x10^-11)(1.673x10^-27)^2 ) / (1x10^-14)^2 = 1.866x10^-36

For the electrostatic force:

(1.6x10^-19)^2 / ( 4pi(8.85x10^12)(1x10^-14)^2 ) = 2.302

2.302 / 1.866x10^-36 = 1.234x10^36

circular path, the magnetic force experienced on the electron acts centripetally as it's always 90 degrees to the direction of the path of the electron, (as well as 90 degrees to the direction of the field)