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# Official OCR A G481 mechanics 20th May 2013 Watch

1. (Original post by Kakashidude101)
What i did:
First part = mgh
Second Part = mgh/45
Third part = (mgh/2) * 0.3

Cos output power was mgh(i think), input / output * 100 = 30, so output * 0.3 = input
Output = Input * 0.3 NOT the other way around. Sorry :/ (You should've realised that input can't be less than output).
2. (Original post by Boy_wonder_95)
Yes!
omg me too!!
3. did you have to work out the gradient? i thought i should do that, but theyve never asked for that before... so i used suvat. v=u+at but my answer was 33... :/
4. (Original post by Joeyoh9292)
GODDAMNIT! I've just realised I dropped at least 4 marks (converting cm^3, missing %, saying grav pe goes to ke in oil (what was the answer to that then?) leaving ratio as 25/9 (which I think will be fine - if it's right), not realising about stress/strain graphs), maybe 5-6.
What is this missing % you speak of?
5. (Original post by MikeyP96)
for the stress strain graph, i put because strain is inversely proportion to the length, if he length is doubled hen the stain is halved which would give the graph a steeper gradient, is that wrong?
That's exactly what I put. Sadly, it appears to be wrong. Stress/Strain graphs don't change for the same metal, apparently. I still don't understand this. Teachercol, mind explaining ?
6. (Original post by Arun1323)
did you have to work out the gradient? i thought i should do that, but theyve never asked for that before... so i used suvat. v=u+at but my answer was 33... :/
You had to draw a tangent to the curve.
7. (Original post by MikeyP96)
for the stress strain graph, i put because strain is inversely proportion to the length, if he length is doubled hen the stain is halved which would give the graph a steeper gradient, is that wrong?
that's what i put but lots of people are saying it's wrong... :/ so idk...
8. (Original post by SamBBB)
Stupid how easy all the mock are compared to these two exams, we have just been an unlucky year!
Yeah:/ Although the June papers usually are harder than the January ones...and that fact that they've scrapped Jan exams now doesn't help!
9. (Original post by Boy_wonder_95)
What is this missing % you speak of?
Stress/Strain graph. Strain was % and Stress was GPa. I forgot both of these, so although I got 1.825, my x10^(whatever) was completely wrong. I dropped a mark.
10. I dropped about 10 marks minimum all down to my stupid mistakes and running out of time. I want to retake this unit already

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11. (Original post by ss2012)
I dropped about 10 marks minimum all down to my stupid mistakes and running out of time. I want to retake this unit already

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I reckon I have done worse than in the January exam (which wasn't good either). Luckily I am dropping physics at the end of this year, but even so, I don't want to be getting D's in my resit, I want to be getting As like in the mocks! WHY ARE THE MOCKS SO MUCH NICER?!
12. Damn, I though I did really well, but I've just realised the mistakes I've made :/ :/ :/ Definitely flopped this paper.

Ah, and would you still get marks for proving kinetic energy with substituting in s=0.5(u+v)t ?
13. (Original post by MikeyP96)
for the stress strain graph, i put because strain is inversely proportion to the length, if he length is doubled hen the stain is halved which would give the graph a steeper gradient, is that wrong?
Yes it is.

If the length is doubled, the est doubles so strain is same.

Graph is same.
14. (Original post by teachercol)
Yes it is.

If the length is doubled, the est doubles so strain is same.

Graph is same.
15. (Original post by brawlerpit)
Damn, I though I did really well, but I've just realised the mistakes I've made :/ :/ :/ Definitely flopped this paper.

Ah, and would you still get marks for proving kinetic energy with substituting in s=0.5(u+v)t ?
that's what i did... ugh better be.. :'(
16. i couldnt do the E=1/2mv^2 question so i lost 4 marks there ( unless they let me have E= f *d instead of s, which i doubt they will)
and a further 2 marks if the stress strain graph question was wrong
17. (Original post by teachercol)
Yes it is.

If the length is doubled, the est doubles so strain is same.

Graph is same.
What do you mean "the est doubles"? Is that a mistype? And how does doubling length affect other aspects?
18. (Original post by teachercol)
Yes it is.

If the length is doubled, the est doubles so strain is same.

Graph is same.
but i thought since strain=extension/length that is the length doubles then the strain is halved?
19. Last question= Rubber?
20. (Original post by teachercol)
I've done the paper. I'll type it up and post it tomorrow.
Do you happen to have the raw mark caps for 100ums from the previous past papers?

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