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

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Original post by CD223
What did you drop marks on?


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everything, didn't revise enough, was too focused on my maths exams. Only wrote a line for 6 marker.

wbu?
What was the correct answer to why it doesn't reach 1.4m? I put there is air resistance resisting the vertical motion and also energy is lost in the circuit due to resistance
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Original post by chizz1889
image.jpg


ooohhh Thank you soo much... i thought i completely flopped this Q but it was just me using r^2 for potential but i am pretty sure i got x10^-5 in the exam. :biggrin:
Original post by SuperMushroom
yep


how did you do that question i did v/r which gives the angular speed in radians (i got something like 5 radians per second) then converted it into degrees and got like 340 degrees. Also i checked my answer by finding the percentage of the circumference it would move if the circumference was a straight line and then found the angle from this
Original post by dominicwild
Yep, people are saying that rather consistently. 130/131 different degrees of significant figures though. Probably won't effect the mark at all.


Nice.

did you get 4R on mc anywhere? the 2 spheres with radius R
Original post by salicional
The first part of the question used a 150Ω resistor, and the second part a 300,000Ω resistor. This lead to a graph that could not be drawn accurately, as it had to start at 1/2000th of the height of the original line! Clearly they missed a 'kilo' off the 150Ω, or added one in on the 300kΩ

I noticed that, just drew it much lower down (below half fwiw) and presumed it wasn't a relative scale, even though it must be or the first graph wouldn't be right haha. Yeah, stupid question.
lol wait for the Q = 30nC question you didn't have to do any fancy stuff all you needed was to find the PD from the graph using the r values given - so you get 750V.

Used W = QV with the 60nC charge and thats the work done...it was only like a 2/3 mark question :redface:
Original post by DanielWall96
how did you do that question i did v/r which gives the angular speed in radians (i got something like 5 radians per second) then converted it into degrees and got like 340 degrees. Also i checked my answer by finding the percentage of the circumference it would move if the circumference was a straight line and then found the angle from this


You just multiply the rad/s by the time, then change it into degrees
Original post by ubisoft
Yesss I need every mark i can lol, did you use BANwsinwt anywhere and get like 0.06 i think?


I used that equation but can't remember my answer. I thought they gave you the time period for 50 full circles (100) so after finding T I forgot to halve it even though I halved the value for f when subsituing 2nf!!! Stupid me!!!
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CD223
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Original post by ubisoft
Nice.

did you get 4R on mc anywhere? the 2 spheres with radius R


I did. Looks like you didn't flop!


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For the capacitor graph, was it above or below their original curve?
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CD223
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Original post by Kennethm
lol wait for the Q = 30nC question you didn't have to do any fancy stuff all you needed was to find the PD from the graph using the r values given - so you get 750V.

Used W = QV with the 60nC charge and thats the work done...it was only like a 2/3 mark question :redface:


Yeah that's what I did lol.


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Amanzz! Hey, hmmm. I agree with the other guys answer I think, smaller reduction in velocity/deceleration is less for given drag force etc. How did you find the paper?
Original post by CD223
I did. Looks like you didn't flop!


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Yes by taking two radius away from 6!
Original post by ubisoft
You just multiply the rad/s by the time, then change it into degrees


i cant really remember the paper but didnt ask for the angle turned in 1 sec given the radius and tangential velocity
Original post by chizz1889
What was the correct answer to why it doesn't reach 1.4m? I put there is air resistance resisting the vertical motion and also energy is lost in the circuit due to resistance


internal resistance of circuit and in practice you can't always assume the mass will remain perfectly vertical - It may sway from left to right causing additional forces.
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Original post by ubisoft
For the capacitor graph, was it above or below their original curve?


I thinks it was below...bigger resistance, less current, hence smaller area, but started and finished at same places cos same pd :teeth:
Original post by DanielWall96
i cant really remember the paper but didnt ask for the angle turned in 1 sec given the radius and tangential velocity


i can't remember too tbh only had 5 mins left when i started Q5 I wasn't even reading the whole question haha
Grade boundaries lower this year compared to last year? I've definitely dropped 8, 4 on the damping one, 3 on the electric fields and i got the scales question as 0, any predictions on UMS?
Original post by CD223
Yeah that's what I did lol.


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I use the term relatively :biggrin:

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