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# OCR M3 (non MEI) Wednesday 8th June Watch

1. (Original post by Miracle-)
2/7 seconds from suvat. t = root(0.8/9.8)

3/4 of a period so 3/4 * 2pi/root98 = 0.476 s

the first bit from 0.075 above to 0 = sin-1(0.075/0.225)/root98 = 0.034s

most likely something wrong, how did you do it?
I used a suvat to find the time for Q to reach P, which was t=2/7

Then I used x=0.225cos(wt), where w=7root(2)

with x=-0.075 to find the time to reach the bottom, which gave t=0.193

and x=-0.1 to get to the point where it is no longer in SHM, which gave t=0.205

v^2=98(0.225^2-0.1^2) to find the velocity leaving SHM, which gave v=2.00

Then another suvat to find the time until it is instantaneously at rest, which gave t=0.204

The sum of the above is t=0.888
2. [QUOTE=drandy76;65562723]One of the was the linear motion with variable forces question, the other was either impact question or SHM question

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'Other' SHM?? what was on the other SHM question??
3. (Original post by drandy76)
One of the was the linear motion with variable forces question, the other was either impact question or SHM question

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and do you remember the variable forces result? I remember getting a minimum and maximum velocity of like -3.5 and +11.5 or something
4. (Original post by Simonium1010)
and do you remember the variable forces result? I remember getting a minimum and maximum velocity of like -3.5 and +11.5 or something
Soz I meant the elastic thingy question, yeah I got those numbers as well

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5. (Original post by Muzzles)
I used a suvat to find the time for Q to reach P, which was t=2/7Then I used x=0.225cos(wt), where w=7root(2)with x=-0.075 to find the time to reach the bottom, which gave t=0.193and x=-0.1 to get to the point where it is no longer in SHM, which gave t=0.205v^2=98(0.225^2-0.1^2) to find the velocity leaving SHM, which gave v=2.00Then another suvat to find the time until it is instantaneously at rest, which gave t=0.204The sum of the above is t=0.888
oh shiit. I forgot about it leaving SHM when its above 0.6m. yeah your way is right.
6. (Original post by drandy76)
Soz I meant the elastic thingy question, yeah I got those numbers as well

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cool. what about the answers to that elastic shm one then??
and which question was the one with the circular motion and find when the string goes slack..?
7. (Original post by Simonium1010)
do you remember what question 2 and 3 were on?
Think Q2 might've been m=0.2, F=3cos(2t).

Think the final answer was 8.77m/s, think Vmax was 11.5 and Vmin was -3.5.

Q3 was P between two strings, max KE was 1.04 I think, x=1/6 where x is extension of left string. Could easily be wrong
8. (Original post by JoeyTr)
Think Q2 might've been m=0.2, F=3cos(2t).

Think the final answer was 8.77m/s, think Vmax was 11.5 and Vmin was -3.5.

Q3 was P between two strings, max KE was 1.04 I think, x=1/6 where x is extension of left string. Couldn't easily be wrong
that's exactly what I got... I messsed up the one with the tension in a circle going slack though, on the part where you gotta find the range of U
9. (Original post by Simonium1010)
that's exactly what I got... I messsed up the one with the tension in a circle going slack though, on the part where you gotta find the range of U
Yeah it was tricky I messed that up slightly, didn't write a lower bound for U so that it reaches the horizon. And in part i I got cos(theta) is 2/3 but then manged to get the height wrong somehow! Tricky business
10. Shall we try putting an unofficial mark scheme together while it's fresh in everyone's head?

I've created a Google doc to get us started: https://docs.google.com/document/d/1...it?usp=sharing
11. (Original post by JoeyTr)
Yeah it was tricky I messed that up slightly, didn't write a lower bound for U so that it reaches the horizon. And in part i I got cos(theta) is 2/3 but then manged to get the height wrong somehow! Tricky business
I'd say I'm on around 57/72.. enough for 80 UMS do you think?
12. (Original post by Simonium1010)
I'd say I'm on around 57/72.. enough for 80 UMS do you think?
I reckon thats about 80-85 UMS yh, maybe more, A* has been as low as 57
13. (Original post by Muzzles)
I used a suvat to find the time for Q to reach P, which was t=2/7

Then I used x=0.225cos(wt), where w=7root(2)

with x=-0.075 to find the time to reach the bottom, which gave t=0.193

and x=-0.1 to get to the point where it is no longer in SHM, which gave t=0.205

v^2=98(0.225^2-0.1^2) to find the velocity leaving SHM, which gave v=2.00

Then another suvat to find the time until it is instantaneously at rest, which gave t=0.204

The sum of the above is t=0.888
Is the velocity leaving the SHM not the same as the velocity entering the SHM due to energy conservation
14. (Original post by XY123)
I reckon thats about 80-85 UMS yh, maybe more, A* has been as low as 57
Yes I'd second that, I reckon it'll be similar to June 2011 boundaries, 52=A, 60=90%
15. I know this probably sounds weird but how did everyone's classmates find it? I was the only person doing it at my school so didn't really get the perspective. I don't really think people on the StudentRoom is a fair sample of how difficult people found the paper generally haha!
16. (Original post by JoeyTr)
I know this probably sounds weird but how did everyone's classmates find it? I was the only person doing it at my school so didn't really get the perspective. I don't really think people on the StudentRoom is a fair sample of how difficult people found the paper generally haha!
There's three of us in my school and I think we all though it was tougher than previous years
17. (Original post by JoeyTr)
I know this probably sounds weird but how did everyone's classmates find it? I was the only person doing it at my school so didn't really get the perspective. I don't really think people on the StudentRoom is a fair sample of how difficult people found the paper generally haha!
Don't think anyone really like this paper, June 2012 grade boundaries needed

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18. (Original post by JoeyTr)
I know this probably sounds weird but how did everyone's classmates find it? I was the only person doing it at my school so didn't really get the perspective. I don't really think people on the StudentRoom is a fair sample of how difficult people found the paper generally haha!
We had about 20 doing it and all found it pretty bad. Average of about 63 marks I'd say, maybe a bit fewer
19. (Original post by JoeyTr)
I know this probably sounds weird but how did everyone's classmates find it? I was the only person doing it at my school so didn't really get the perspective. I don't really think people on the StudentRoom is a fair sample of how difficult people found the paper generally haha!
My college is a good state school; about 20 of us took the exam, 1 found it fine, about 15 thought it was tough and a few were really upset.
20. woudnt the last question involve a phase shift, so a extra constant in the sin bracket since it didnt start at the extreme extension?

i got the amp and other things wrong so il only get about 6 marks total for last question but im pretty sure you needed a phase shift,and im pretty sure it was the first time its ever came up on ocr

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