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# OCR MEI Core 4 (C4 4754/01 and 4754/02) watch

Ok so I thought it was an OK exam.

There seems to be differing answers about the last question. Personally, I put C as, if you re-read the section on accuracy in text, it claimed that even 2 significant figures for the carbon dioxide would be accurate enough.

I realise that the question specifyed a distance though; so I simply put that, since the sig figs were negligible for the carbon dioxide, in this case scenario (and especially if you had wanted to convert the distance into carbon d. mass emissions) the sig figs would also be negligible for miles.

Either way, bit of an ambiguous question.
Yeah, i picked up on that too, so when explaining my reasoning i talked about sig figures...
2. (Original post by OL1V3R)
What did everyone do with the vectors question, where you had to calculate the angle of the pipeline with the vertical? I basically found the dot-product of the pipeline's direction vector with the unit vector in the z-direction and used the formula cosθ = a.b/|a||b| to calculate the angle it made with this unit vector. Would that be a reasonable method?
First of all I started out by thinking "wtf is a verticle?". then i used ab and oz to do the angle formula (300,100,100).(0,0,1)/dot product of root of those. came out with like 52 or something
3. (Original post by Muffinz)
First of all I started out by thinking "wtf is a verticle?". then i used ab and oz to do the angle formula (300,100,100).(0,0,1)/dot product of root of those. came out with like 52 or something
I came out with 72 - just realised that 72 seems to ring a bell more than 52.

The last question on the paper kept tricking me, which I didn't expect, but I got there in the end!

How does everyone think the comprehension paper went?
4. (Original post by OL1V3R)
I think I did as well!

The last question on the paper kept tricking me, which I didn't expect, but I got there in the end!

How does everyone think the comprehension paper went?
I did that (0,0,1) thing too.

Comprehension was fine.

Really struggled with the damn parametric equation - about question 4.
5. Vector questions:

ii) to find the angle between the vertical and direction vector, I'm fairly sure you had to use a vertical direction such that (0,0,z) where z is any positive number as it was the line OZ. No matter what value for z you used, you'd notice that when finding costheta, the two values of z should cancel anyway.

iv) last part; you find the angle between normal direction to the plane and direction of AB. I then took this value away from 90degrees.

Again, not 100% on these, but I'm fairly certain they're right.
Vector questions:

ii) to find the angle between the vertical and direction vector, I'm fairly sure you had to use a vertical direction such that (0,0,z) where z is any positive number as it was the line OZ. No matter what value for z you used, you'd notice that when finding costheta, the two values of z should cancel anyway.

iv) last part; you find the angle between normal direction to the plane and direction of AB. I then took this value away from 90degrees.

Again, not 100% on these, but I'm fairly certain they're right.
Why'd you take it away from 90?
iv) last part; you find the angle between normal direction to the plane and direction of AB. I then took this value away from 90degrees.

Again, not 100% on these, but I'm fairly certain they're right.
I got an angle of 49.9 degrees to the normal, and did what you did as well. But I also added that it is at 41.1 degrees to the plane, in case that's what they wanted.

Boy am I not looking forward to FP2 :|
8. because a plane is 90degrees to the normal.
9. (Original post by Hippysnake)
Why'd you take it away from 90?
See attached, although I am not 100% on this either.
Attached Images

10. LOL I drew that exact picture on some scrap paper during the exam.

Without colours, obviously.
11. (Original post by Hawiz)
See attached, although I am not 100% on this either.
As far as I remember the question said "calculate the angle at which the pipeline intersects the layer" so I think that probably meant the angle to the plane.
12. I though this was a well nice paper. Nasty comprehension trying to trick you with conversions of miles when the distances were already in km though... =/

Did anyone do FP3 at the same time?
13. Hmmmm. We shall see.
14. (Original post by foolsihboy)
I though this was a well nice paper. Nasty comprehension trying to trick you with conversions of miles when the distances were already in km though... =/

Did anyone do FP3 at the same time?
No I didn't, but I bet you've had one hell of a day. I would laugh if FP3 was in the afternoon as well.
because a plane is 90degrees to the normal.
I did 180-angle. Though I wasn't sure it was necessary, so I did it in kinda small writing.
16. Does anyone know how they do the UMS scale?

Because I think I did well in the actual paper, but messed up a bit in the comprehension.

Do they add the two raw marks together then convert to UMS, or do they work out a UMS for each paper separately, then add them together?
No I didn't, but I bet you've had one hell of a day. I would laugh if FP3 was in the afternoon as well.
It was =/
18. (Original post by A100whoo)
comprehension was easyish, but the grade boundaries will just be higher making no difference.

paper a was ok, apart from the last question part 1! where you had to show the ratio was true.

what did people get for the parameter values for A and B???

For B I got 4 pi
for A i got pi/2 .....
it cant be those values because it said OA and OB had a ratio of pi-1i+1
which is effectively 1:2
i got B is pi
and A is pi/2

however my working didnt really make sense, so ive no idea how i got that
i duno if its right but it makes sense?
19. This was a brilliant exam
20. (Original post by JoshC)
i dunno! that stumped me lol. i think i put:

say AB =
300
100
100

i used that and
0
0
100

or something
So do you remember what you got as the answer?
I think I used the same method and got roughly 72 degrees - anyone else?

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