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# Math paper 2 watch

1. i expected both papers to be harder! but i still made the stupidest mistakes.. well i found paper one good except the last to .. i just put some random stuff.. and vector projection.. wat the hell is that?!
in paper 2 i sooo messed up on the 1st q.. stupid or wat!?!? it was like the give away mark question and i still managed to do it completely wrong.. i coulndt remeber how to do it!.. messed up man.. then i couldnt do the first part of the vectors.. and my induction was a little dodgy.. did ne one do the stats option? it was alright except for the 3rd part the one with the coins.. it was so messed upman.. eveyone in my class did something completely different!! watt he hell was the H1? their null hypothesis was soo messed up..... arg.. still bummed about question 1!!! 14 marks out the window....
2. yeh exactly..forgot bout that.
3. (Original post by akk713)
I remember the rate of c going upwards is 2cm/s
Ok, people, here is the solution, I dunno if it is radians or degrees though.

ds/dt = 2cm/s
[Given in question]

dθ/dt = ds/dt * dθ/ds
[Ordinary algebra]

tan(θ) = s/5cm
[From the definition of tan(θ) ]

s = 5cm * tan(θ)
[Rearranging]

d/ds s = d/ds 5cm * tan(θ)
[Differentiating with respect to s]

1 = 5cm * (cos²(θ)dθ/ds + sin²(θ)dθ/ds)/cos²(θ)
[Quotient rule]

1/5cm = (1 + tan²(θ))dθ/ds
[Using: sin²(θ) + cos²(θ) = 1 ,and sin(θ)/cos(θ)=tan(θ)]

dθ/ds = 1/ (5cm * (1 + tan²(θ)) )
[Solving for dθ/ds]

dθ/ds = 1 / 5cm(1 + s²/5²cm²)
[Substituting tan(θ) = s/5cm ]

s = 5√(3)cm
[Using pythagoras theorem]

dθ/ds = 1 / 5cm(1 + (5√(3)cm)²/5²cm²)
[Substituting s = 5√(3)cm ]

dθ/ds = 1 / 5cm(1 + 3) = 1/ 20cm
[Simplifying]

dθ/dt = 2cm/s * 1/20cm = 0.1/s
[Substituting into the expression for dθ/dt]

I cant see any reason why this answer should neccessarily be radians and not degrees though... Except perhaps if you say that rad = cm/cm and that degree = 360/2pi cm/cm.
4. well i have to get my points up from the other exams now
5. Thanks for that Jonatan..at least i know i got two questions correct in paper two.. (coincidentally 19 and 20)

you know another mistake i just realised i made: the question where

|(x+9)/(x-9)| <= 2 (not 100% sure on these numbers bt similar)

i only put that x was less than or equal to 3, didnt check for greater values - turns out x greater than or equal to 27. damn. How many marks u think i lose here?

[R] i feel your pain man i did exactly the same mistake in paper 2 question 1!
6. (Original post by portugal)
Thanks for that Jonatan..at least i know i got two questions correct in paper two.. (coincidentally 19 and 20)

you know another mistake i just realised i made: the question where

|(x+9)/(x-9)| <= 2 (not 100% sure on these numbers bt similar)

i only put that x was less than or equal to 3, didnt check for greater values - turns out x greater than or equal to 27. damn. How many marks u think i lose here?

[R] i feel your pain man i did exactly the same mistake in paper 2 question 1!
LOL. I lost half the marks there as well because I solved (x+9)/(x-9) rather than |(x+9)/(x-9)|. Also, I suspect the vector projection question may be wrong as I dont really know how to do it I just guess that it was the dot product divided by the magnitude of the vector it was projected at times the unit vector.
7. argh must say i regret having discussed the paper with people!ive realised how many ive actually messed up due to sheer stupidity!arghh!
8. (Original post by portugal)
argh must say i regret having discussed the paper with people!ive realised how many ive actually messed up due to sheer stupidity!arghh!
On the second hand you dont need a full score to get a 7. I am mainly worried about my physics. Anyone know aproximately where they set the grade limits for 6es and 7s in Physics HL ?
9. can someone please explain to me how they found the rotations of the pedal, in that stupid bicycle question in Maths Methods Paper 2???????????????????? and what was the answer to the last part? the equation of the other pedal???????????
10. yea the a and b values
11. (Original post by Cordy_star)
can someone please explain to me how they found the rotations of the pedal, in that stupid bicycle question in Maths Methods Paper 2???????????????????? and what was the answer to the last part? the equation of the other pedal???????????
There there. Take a deep breath and then we can try to make some sense out of this. I have not seen teh question, but here are some tips which might work.

1: The angular distance traveled by a pedal in one revolution is 2pi radians.
2: The linear distance is simply teh radius times the angular distance. Thus if the pedals are 15cm from the axis then this is 30pi cm.

3:velocity is distance divided by time.
4:The two pedals are separated by pi radians (They are on opposite sides).
12. in 2003 grade boundaries were 64% for a 6 and..75%(i believe not completely sure) for a 7
13. Is it that simple? duh, how could i be so stupid...ofcourse, it was only worth like 2 marks
Thanks jonatan
14. (Original post by portugal)
in 2003 grade boundaries were 64% for a 6 and..75%(i believe not completely sure) for a 7
DAMN! Then I am on the limit of a 7 despite the fact I missed one entire question on paper 2 (I only did one at section B). Thanks man, you really helped me sleep there. Do you knwo how much it varies from year to year ?
15. (Original post by Cordy_star)
Is it that simple? duh, how could i be so stupid...ofcourse, it was only worth like 2 marks
Thanks jonatan
I have not seen teh question so I dont know if this was all of it. If it is moving forwards then you have to add that translational motion to the function. If you could give me the question I could try to do it.
16. not too sure on how it varies every year sorry..normally its around that though
17. Did anyone do the stats option on the paper? and if they did, could they do the last part of the question, the one about the trees? If so could they explain it to me please?
18. (Original post by Jonatan)
I have not seen teh question so I dont know if this was all of it. If it is moving forwards then you have to add that translational motion to the function. If you could give me the question I could try to do it.
No, i think that is it, because it wasn't in motion. thanks
19. (Original post by Cordy_star)
Did anyone do the stats option on the paper? and if they did, could they do the last part of the question, the one about the trees? If so could they explain it to me please?
I only know the stats which is part of teh HL syllabus. If you have anything on the normal distribution I may be able to help
20. (Original post by Jonatan)
Ok, people, here is the solution, I dunno if it is radians or degrees though.

ds/dt = 2cm/s
[Given in question]

dθ/dt = ds/dt * dθ/ds
[Ordinary algebra]

tan(θ) = s/5cm
[From the definition of tan(θ) ]

s = 5cm * tan(θ)
[Rearranging]

d/ds s = d/ds 5cm * tan(θ)
[Differentiating with respect to s]

1 = 5cm * (cos²(θ)dθ/ds + sin²(θ)dθ/ds)/cos²(θ)
[Quotient rule]

1/5cm = (1 + tan²(θ))dθ/ds
[Using: sin²(θ) + cos²(θ) = 1 ,and sin(θ)/cos(θ)=tan(θ)]

dθ/ds = 1/ (5cm * (1 + tan²(θ)) )
[Solving for dθ/ds]

dθ/ds = 1 / 5cm(1 + s²/5²cm²)
[Substituting tan(θ) = s/5cm ]

s = 5√(3)cm
[Using pythagoras theorem]

dθ/ds = 1 / 5cm(1 + (5√(3)cm)²/5²cm²)
[Substituting s = 5√(3)cm ]

dθ/ds = 1 / 5cm(1 + 3) = 1/ 20cm
[Simplifying]

dθ/dt = 2cm/s * 1/20cm = 0.1/s
[Substituting into the expression for dθ/dt]

I cant see any reason why this answer should neccessarily be radians and not degrees though... Except perhaps if you say that rad = cm/cm and that degree = 360/2pi cm/cm.
thanks Jonatan

I actually did using the same method...

that's why I never ponder whether it's in radians or degrees
cause in solving dimentional problems I always work in degree!!

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