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# OCR Advancing Physics G492 ~5 June 2013~ watch

1. (Original post by ArchieL)
With the trolley on the ramp, it has an acceleration, g, acting directly downwards. If we take the component of this force parallel to the plane (using the cos rule, as it's an enC(os)losed angle), we get a=(9.81)(sin(theta)) => a=g.sinϴ

If we then substitute this into the equation v2=u2+2as with u=0, we get that result (v2 =2.g.l.sinϴ). Also it's probably worth noting that plotting a graph with v^2 against sinϴ gets us with a gradient of 2.g.l
Thank you so much!! It's frustrating that there are so many mathsy questions which I suck at
2. (Original post by marseille_h)
Antinodes is where the intestity is the highest compared to nodes where it is =0
Thank you!
3. The opening questions of the physics paper is normally units.....(E.g 1J=1Nm)
Can someone post as many of these types of equations and units that can come up??
4. Timing recommendations for each section?
5. (Original post by oliver_h)
timing recommendations for each section?
a 20
b 40
c 60
6. (Original post by gary96)
a 20
b 40
c 60
b and c are the same amount of marks, so i like to do 40 40 and leave 20 mins for checking.
7. (Original post by vithusan40)
The opening questions of the physics paper is normally units.....(E.g 1J=1Nm)
Can someone post as many of these types of equations and units that can come up??
Just think equations!
Force (N) = ma = kgms^-2
Work (J) = Fd (Nm, Kgm^2s^-2)
Power (J/s) = Fv = Js^-1 = Nms^-1

etc etc
8. (Original post by Mathletic)
I actually did this experiment for my coursework!! however I decided to prove the relationship between acceleration and displacement but I used exactly the same set up!
Your absolutely right with the length of the card, this influences the data hugely, especially at lower speeds where the trolley passes the light gate the card just distorts the data - it prevents the true speed to be detected.
To reduce this systematic error you can shorten the length of card but if its too thin the light gate wont detect it!!!

The friction on the ramp also influences the speed the trolley travels down the ramp, of course you want to reduce resistance so reduce surface area of wheels and use a smoother ramp perhaps?

As for the angle this was the hardest part to get right in my experiment, primarily due to paralax errors distorting the true angle, I used a larger protractor to get my angle so i could align the ramp and the radii of the protractor, this is more accurate than using a small protractor, I also experimented using trigonometry because you know all the lengths! this was very boring and time consuming so I just used protractor in the end!

Im also thinking the light gate must be calibrated properly to avoid zero errors? They may get us to plot a graph based on v^2 = u^2 +2as?

Oooh and one last thing, ensuring the trolley goes STRAIGHT down the ramp! Probably wont be asked but mine had a wonkey axel so I had to mend it!
Really great post. You say that the size of the card caused problems in the result, why do you think a larger card created bigger errors? Was it because the trolley had accelerated a little more by the time it cleared the light beam, or do you think its something else.
9. With the Pre-Release material, what are the key points we should prepare for before the exam?
10. Well the light gateworks by sensing a sudden change in light, if you imagine moving a pencil through a light gate fairly slowly you could get a reading of say half 0.1 ms-1, the light gate noticed that something passed and covered the sensors on the light gate, so you may get a reading of say 0.13 ms-1

Now if you moved a piece of card which is much longer than the penceil (width) and if you moved that past the light gate at 0.1ms-1 as well... both objects are ACTUALLY moving at 0.1ms-1 but because of the added length to the card the sensor is covered up longer,

The lightgate now thinks Ahh this is a slow object because the sensors have been covered up longer! Does that make sense its hard to describe,

Similarly if you moved a piece of wood thats a meter long through the lightgate at 10ms-1 the sensors would be coverd up the same amount of time as a block moving past very slow, they will both give the same reading on the light gate but there ACTUAL speeds are different

It all whittles down to speed distance time, we had a data logger which required you to enter the width of the object passing through it to avoid this error, (ie calibrating it)

SORRY MEANT TO QUOTE THIS TO REEBOP
11. Well it's bed time now.. See you on the other side folks.

12. (Original post by vithusan40)
With the Pre-Release material, what are the key points we should prepare for before the exam?
Have a look at my earlier post with links to prerelease questions, it may help
13. (Original post by ArchieL)
Well it's bed time now.. See you on the other side folks.

Best of luck and thanks for the pre release material!
14. (Original post by reebop)
Really great post. You say that the size of the card caused problems in the result, why do you think a larger card created bigger errors? Was it because the trolley had accelerated a little more by the time it cleared the light beam, or do you think its something else.
sorry i replied but forgot to quote its somewhere on this page i think :P

might be usefull
16. Everyone check graph units before calculating gradients etc especially on section c good luck all !!!
17. (Original post by Tejmasta)
Anyone else think the section c questions are not really physics?
Not really it's applied. G491 was a bunch of non physics, not section c of G492 with "estimate the number of pages in an ebook", and " how many beats per minute does this ecg show". etc
18. I have never heard of pre release questions? Is it posted by OCR itself? What does that mean??
19. (Original post by walkers38)
I have never heard of pre release questions? Is it posted by OCR itself? What does that mean??
Yeah check their site although you really should have looked at it before :/

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20. What is the equation with Work function in it?

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