The Student Room Group

EDEXCEL A2 Physics EXAM Unit 4 Physics On The Move 20th June 2016 (NOT I-A-L)

Scroll to see replies

Original post by oShahpo
r = mv^2 / F sin22 .


can someone please verify this for this question:


was the force labeled in the diagram (from friction or whatever was in the question) just the frictional force or the resultant (centripetal force)
basically what im asking is, is that force in the diagram F= mv^2 / r
or is the centripetal force the horizontal to that?
Original post by jtebbbs
Yeah I always try to in physics


also did you get 20% for max?
Does anyone know if there is an unofficial mark scheme anywhere?
Reply 223
One of the questions was about why the silicon plate had such a small capacitance, anyone remember what they answered for that?
Original post by Ilaawef
One of the questions was about why the silicon plate had such a small capacitance, anyone remember what they answered for that?


I said that it was to do with the time constant (RC) needing to be low but I'm not sure if that is correct?
Original post by Ilaawef
One of the questions was about why the silicon plate had such a small capacitance, anyone remember what they answered for that?

small rc so discharges quickly, also holds less charge so more sensitive.
Reply 226
Original post by funkyfig
I said that it was to do with the time constant (RC) needing to be low but I'm not sure if that is correct?


I'm not sure myself, I didn't actually get to answer it because it was confusing. All I remember was the question stating it needs to detect minute changes in the distance. Probably because silicon is used in sensitive circuits?
Reply 227
Original post by oShahpo
small rc so discharges quickly, also holds less charge so more sensitive.


Ah alright, I guess I was somewhere on the right track, I just ran out of time going over questions I skipped.
Original post by lauren con
I got 80% too! doesn't seem like many people got the same though


Me too! Though I wasn't particularly confident about it, it made the most logical sense to me that it would be the way to go about that question.
Original post by ajaxkiller
can someone please verify this for this question:


was the force labeled in the diagram (from friction or whatever was in the question) just the frictional force or the resultant (centripetal force)
basically what im asking is, is that force in the diagram F= mv^2 / r
or is the centripetal force the horizontal to that?


to find r isn't it?

Fsin22 = mv^2/r
Fcos22 = mg

tan22=v^2/rg

That's what I did anyway??
Original post by kidlikethat
to find r isn't it?

Fsin22 = mv^2/r
Fcos22 = mg

tan22=v^2/rg

That's what I did anyway??


they gave you the mass of the guy in the question, your method ignores mass, surely if they wanted you to eliminate mass, they wouldnt have given it to you in the first place.....
Original post by ajaxkiller
they gave you the mass of the guy in the question, your method ignores mass, surely if they wanted you to eliminate mass, they wouldnt have given it to you in the first place.....


No, they gave you the mass so that you don't get confused and so that you can follow the straight forward method. Eliminating the mass is acceptable as circular motion never depends on the mass anyway.
Im having a bloody fit over here because I keep getting 20.5m for the radius but everyone is getting 20.4m
is there any vote on how people found it/grade boundaries?
Original post by student143
is there any vote on how people found it/grade boundaries?


http://www.thestudentroom.co.uk/showthread.php?t=4176400
What do you think the grade boundaries will be ? Also has anyone got an unofficial mark scheme yet ?
Reply 236
Original post by Salty carpet
Im having a bloody fit over here because I keep getting 20.5m for the radius but everyone is getting 20.4m


thats because you are using g as 9.8 and not 9.81
Original post by linaxq
thats because you are using g as 9.8 and not 9.81


Do a-level maths they said, it'll help you with physics they said
Reply 238
Original post by Salty carpet
Do a-level maths they said, it'll help you with physics they said


lmao i did the same thing but i went back a realised.
Reply 239
Original post by Jordan97
You had to find the charge difference when the plates were at 3.5mm and 4.2mm, not 2.8mm and 4.2mm


i agree because it was asking about the maximum charge decrease allowance charge only decreases when the d increases.

Quick Reply

Latest