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

Original post by cricket66

restoring force is minimum at the centre of oscillation.

I'm pretty sure it asked for 'resultant' not 'restoring' force.

Original post by FrightBright

A* 57

A-50

B-45

I dont know :biggrin:

What did people get for the work done from the two points...

I got 1.92x10^-10 joules exact.....

Anyone?

If I get this dropped marks in written is about 15 -.-

This had to be harder than June 10 which would make A boundary at least lower than 48.

Reply 782

justanotherposter

Original post by Sam-8

what did people get for the multiple chpice question of the 3 materials and the magnet? which order out of copper, iron and rubber i think they were :/

Can't remember the order but I think it went from lowest to highest resistivity (I hope.)

Any reason why people are voting an A will be about 50 marks? The lowest it's ever been is 48, and this paper is a lot harder than anything I've seen before.

Reply 783

Original post by rub em out

I cant remember the wording of the options but I put something along the lines of when the power supply is turned off because then the rate of change of flux linkage would be the greatest?

That's what I put too, think it's right.

Reply 784

cricket66

Original post by icedragon

I'm pretty sure it asked for 'resultant' not 'restoring' force.

This had to be harder than June 10 which would make A boundary at least lower than 48.

bugger, thanks for pointing it out! textbook error, RTFQ!

Reply 785

Original post by Sam-8

haha alright, i think i did the same. so first to hit was the one through rubber, the lead then copper?? or the other way?

I did rubber first then the next two lowest or highest or whatever blah

Reply 786

SmithytheDrummer

Original post by icedragon

I'm pretty sure it asked for 'resultant' not 'restoring' force.

I was wondering about this, like at the centre I just presumed that the tension of the spring is less than at any point if it was compressed or stretched.

Reply 787

I think I got PQR (rubber, something, something)

'Electrical resistivity (also known as resistivity, specific electrical resistance, or volume resistivity) is a measure of how strongly a material opposes the flow of electric current'

So the one with the highest Resistivity would experience almost no induced current, hitting the ground first (rubber) and the one with the lowest would experience the most induced current and force against its movement?

Reply 788

Original post by Benniboi1

Same, just to confirm I think it was D?

Reply 789

Original post by Aristotle's' Disciple

Same, just to confirm I think it was D?

That sounds about right, in fact yeah I'm sure it was D.

Reply 790

jamesrichardkilby

Surely there would be the largest change in flux whilst the current is changing?

This was posted from The Student Room's Android App on my HTC Incredible S

Reply 791

Original post by Benniboi1

That sounds about right, in fact yeah I'm sure it was D.

Awesome, for the last multiple choice Q I worked out the Voltage by subbing in the values with efficiency as 0.15, rearranging and then multiplying by 0.15, I can't remember what I got though. >.<

Reply 792

paul272

i knw its been asked before, but was the resultant force one a minimum at the bottom, centre or top, i put centre, because a=0, and therefore f=0, also for the 6 marker, what do people think will need to be written... i only wrpte like 3 points, i completely ran out of time

Reply 793

FrightBright

Original post by Aristotle's' Disciple

Awesome, for the last multiple choice Q I worked out the Voltage by subbing in the values with efficiency as 0.15, rearranging and then multiplying by 0.15, I can't remember what I got though. >.<

i got A 4.9

Reply 794

justanotherposter

Original post by SmithytheDrummer

I was wondering about this, like at the centre I just presumed that the tension of the spring is less than at any point if it was compressed or stretched.

Wouldn't no resultant force mean there is no acceleration on the body? In which case it would be at the centre.

Reply 795

Original post by FrightBright

i got A 4.9

I can't remember what I got, only the method, do you remember the values? I could redo it lmao.

Reply 796

I put an A as 50 because although it was hard it wasn't impossible, I thought the paper in Jan was hard and it was one of the higher grade boundaries, I just can't see the grade boundary changing that much, 48ish minimum

Reply 797

Original post by jamesrichardkilby

Surely there would be the largest change in flux whilst the current is changing?

This was posted from The Student Room's Android App on my HTC Incredible S

From what I understand magnetic flux is greatest when the rate of change of current is greatest. If you think about it, this is greatest when the current is turned off (at that point it had the greatest current, going to 0 pretty fast).

Reply 798

Original post by SmithytheDrummer

I was wondering about this, like at the centre I just presumed that the tension of the spring is less than at any point if it was compressed or stretched.

If I remember it was asking for the point at which the resultant force on the mass was at a minimum. This would be at the bottom because at that point mg is acting down but tension (or restoring force from the spring) is acting up, whereas at the top they are both acting down and in the centre it's just mg acting down. So the bottom would be minimum.

Original post by justanotherposter

Wouldn't no resultant force mean there is no acceleration on the body? In which case it would be at the centre.

Resultant force includes mg, read above.

Reply 799