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HL Math Paper 2- 24 Hours Later...

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    How did you all find it? Let's share answers, people! :P
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    What did you get for the applications question? Writing an equation for v in terms of t?
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    (Original post by johndoe04)
    What did you get for the applications question? Writing an equation for v in terms of t?
    I got v=arctan(pi/4-t)
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    Q1)a)
    a=2
    d=3/2
    b)
    n=28

    Q9) (that circle one where they gave loads of space to answer the question)

    67.5 (approx)

    I should be able to salvage more soon ^^.
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    For the ball bouncing did you guys use ar^n or ar^n-1 there was a bit debate in my school about it ^^.
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    The question said the distance the ball reached after its bounces so after its first bounce it should have been 3.8m not 4 as ar^n-1 suggests.
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    (Original post by Hyaline)
    For the ball bouncing did you guys use ar^n or ar^n-1 there was a bit debate in my school about it ^^.

    n-1.

    Nooooooooooooooooo. Arctan? How? urghhhhh

    I thought that v^2 = dv/dt since they're both acceleration? :/
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    (Original post by Saymyname!)
    I got v=arctan(pi/4-t)
    can you help me understand how you got that? I remember thinking that you couldn't just integrate straight away.....
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    if you got v^2 you rearranged it wrong at the start :P.
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    (Original post by Hyaline)
    if you got v^2 you rearranged it wrong at the start :P.
    The equation was something like, v^2 +dv/dt - 1 = 0. How did you go from there?
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    In the bouncing ball question n was the number of bounces right ^^.
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    (Original post by Hyaline)
    if you got v^2 you rearranged it wrong at the start :P.
    I said that since velocity is ds/dt, then v^2 is d^2s/dt^2 which equals acceleration. And dv/dt is also acceleration. At the time, i thought it made sense. Although....yeah, when i left the exam hall, i felt that maybe it wasn't correct. Urgghghghghghghghghghg
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    (Original post by Hyaline)
    In the bouncing ball question n was the number of bounces right ^^.
    Yup.

    Sigh. At least i got that one correct.
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    you get 1/1-v^2 dv=dt then integrate both sides according to the equation you posted....... I don't remember whether there were boundaries.
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    (Original post by Hyaline)
    you get 1/1-v^2 dv=dt then integrate both sides according to the equation you posted....... I don't remember whether there were boundaries.
    argh. yeah. damn. that makes sense.

    Suddenly, i feel really, really bad.
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    (Original post by johndoe04)
    Yup.

    Sigh. At least i got that one correct.
    Need more opinions on the ar^n ar^n-1 thing. My logic was that if n is the number of bounces, after 1 bounces where n=1, the ball would reach a height of 3.8 not 4, so it works in a similar way to compound interest.

    Initially I assumed that 4 being the first term would equal 4*0.95^(1-1)=4. But if n represents bounces (what else could it represent :P), then after the first bounce the ball wouldn't come back to a height of 4m, it would reach 3.8m sincd the question said 0.95 of the previous height- so I used ar^n instead......... I'm worried about this question now
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    Crossing out the correct answer and putting down the wrong answer is my worst nightmare............
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    (Original post by Hyaline)
    Need more opinions on the ar^n ar^n-1 thing. My logic was that if n is the number of bounces, after 1 bounces where n=1, the ball would reach a height of 3.8 not 4, so it works in a similar way to compound interest.

    Initially I assumed that 4 being the first term would equal 4*0.95^(1-1)=4. But if n represents bounces (what else could it represent :P), then after the first bounce the ball wouldn't come back to a height of 4m, it would reach 3.8m sincd the question said 0.95 of the previous height- so I used ar^n instead......... I'm worried about this question now
    No, wait. Actually, I remember putting 3.8 down after the first bounce since it makes absolute sense that the ball loses energy after the first bounce, and therefore reaches a lower height. Because it will never equal 4.
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    integral of 1/1+x^4 anyone............ I got some long thing with ln and arctan in it, most likely wrong........
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    I asked one of the maths teacher in my school after and she couldn't do it....................

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Updated: May 6, 2012
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