AQA Physics A Unit 4- 11 June 2014

Did anyone else not understand question 13 in section A? it was about two points and the distance between but I couldn't understand what they wanted so I wrote down part of the question: "when the distance between the points is 20mm, the force they exert is 0.5F. what is the distance, d? 7mm, 14mm, 15mm, 28mm."
There was no other information so isn't the distance 20mm as stated..? or am I the only one to misunderstand this..?

SECTION B- Answers I can remember and stuff: CORRECTED

Question 1: Gravitation (14 marks)
1) Vector quantity-- force per unit mass on a small test mass placed a distance r from the CoM of an object (2)
2) derive: g=GM/(R+h)^2 (2)
3) Force= 2450N (3sf) (3)
4) prove time period is around 7.97hrs ish, then say 3 orbits in 24hrs (5)
5) any polar orbitting satellite uses e.g mapping, weather... and explanation (2)

Question 2: Fields (10 marks)
1) Force acts to the left; anthying like direction of field is N-->S, attracts positive side, opposite charges, all of that (2)
2) Use F= Wd/distance, forgot number sorry :/ (2)
3) Use E= F/3e, again forgot number soryy (1)
3) Force acts downwards, must be perp. to direction of current and field, apply Flemmings left hand rule (2)
4) proof of number of electrons, normal (1)
5) B= 0.16T ; could have worked out with BIl or BQv (2)

Question 3: SHM (14 marks)
1) elastic and gravitational potentials (1)
2) This was bit tricky, depends on where you said GPE= 0, but general concept is or normal SHM, maybe mention air resistance and friction which could cause energy loss too (2)
3) time period= 0.8s, general explanation about number of maximums or number of times total potential= 0 (2)
4) draw -cos graph, should have had 1.5 waves (2)
5) k=21.6 N/m (3)
6) prove its 43mm i think i got (4)

Question 4: Capacitors (12 marks)
1) C= 61.3 x 10^-6(3)
2) R= 8.4 x 10^5 (3)
3) 6 marker: Could talk about, flow of electrons from B to A, rate of flow decreases with time, V of capacitor increase with time, V or resistor decreases with time, when fully charged, V on capacitor= same as pd supply and that on R is 0. Electric energy--> KE to move electrons--> chemical in storage in capacitor. When switched moved, voltage, current and charge over capacitor drops...and more but too much typing

This confused me so much, I just thought 'they've answered their own chuffing question here'

Then I realised that that was the distance for 0.5F and they wanted the distance for F (1F).
I think I ended up dividing 20 by root 2 (as force is proportional to 1/r^2) so kinda inversed it all? It came out as 14.142.... so just assumed it was 14.
Took me ages though to understand what it wanted me to do aha!

SECTION B- Answers I can remember and stuff: COPIED

Question 1: Gravitation (14 marks)
1) Vector quantity-- force per unit mass on a small test mass placed a distance r from the CoM of an object (2)
2) derive: g=GM/(R+h)^2 (2)
3) Force= 2450N (3sf) (3)
4) prove time period is around 7.97hrs ish, then say 3 orbits in 24hrs (5)
5) any polar orbitting satellite uses e.g mapping, weather... and explanation (2)

Question 2: Fields (10 marks)
1) Force acts to the left; anthying like direction of field is N-->S, attracts positive side, opposite charges, all of that (2)
2) Use F= Wd/distance, forgot number sorry :/ (2)
3) Use E= F/3e, again forgot number soryy (1)
3) Force acts downwards, must be perp. to direction of current and field, apply Flemmings left hand rule (2)
4) proof of number of electrons, normal (1)
5) B= 0.16T ; could have worked out with BIl or BQv (2)

Question 3: SHM (14 marks)
1) elastic and gravitational potentials (1)
2) This was bit tricky, depends on where you said GPE= 0, but general concept is or normal SHM, maybe mention air resistance and friction which could cause energy loss too (2)
3) time period= 0.8s, general explanation about number of maximums or number of times total potential= 0 (2)
4) draw -cos graph, should have had 1.5 waves (2)
5) k=21.6 N/m (3)
6) prove its 43mm i think i got (4)

Question 4: Capacitors (12 marks)
1) C= 61.3 x 10^-6(3)
2) R= 8.4 x 10^5 (3)
3) 6 marker: Could talk about, flow of electrons from B to A, rate of flow decreases with time, V of capacitor increase with time, V or resistor decreases with time, when fully charged, V on capacitor= same as pd supply and that on R is 0. Electric energy--> KE to move electrons--> chemical in storage in capacitor. When switched moved, voltage, current and charge over capacitor drops...and more but too much typing

there was this qn in mcq: at a certain voltage, energy= 1600 microjoules and V-2=400 microjoules. I think the answer was 200 microfarads. Does anyone remember what question number this was? Really freaked out cause I think my shading got mixed up. Thanks!

It said what is the distance for force F, i got 14mm

That was 20mm for 0.5F. Need to work it out for F.

Couldn't do it so guessed it

chuffing hell mate, that's what i put too!!!

Ha! I wish it had gone badly. This was way worse than bad.

The force on the electrons is definetly out of the page. They specifically asked for force on electrons not wire so second finger must be in opposite direction to current

My markscheme page 73 >>>>> this bs because you copied me ffs :P

He posted his first draft on page 66. Please have some respect.


Posted from TSR Mobile

He posted his first draft on page 66. Please have some respect.


Posted from TSR Mobile

He found out his version was ****, so copied that guys...

He found out his version was ****, so copied that guys...

Still downwards ... ... The wire only moves downwards due to a downwards force on the electrons ....


Posted from TSR Mobile

i knew the formula for orbital period, but i didnt get the right answer for some reason so what i did is turn 8 hours to seconds, then i put my formula= what 8 hours in seconds is, do you think i could have conned the examiner

He found out his version was ****, so copied that guys...

My markscheme page 73 >>>>> this bs because you copied me ffs :P

hahaha well, if you check page 67 youll see that mine was first. so erm, im expecting an apology for that

hehe dw, seems like we got the same stuff soo not complaining