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HL Math Paper 2- 24 Hours Later...

How did you all find it? Let's share answers, people! :P

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Reply 1
What did you get for the applications question? Writing an equation for v in terms of t?
Reply 2
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)
Reply 3
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 ^^.
Reply 4
For the ball bouncing did you guys use ar^n or ar^n-1 there was a bit debate in my school about it ^^.
Reply 5
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.
Reply 6
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? :/
Reply 7
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.....
Reply 8
if you got v^2 you rearranged it wrong at the start :P.
Reply 9
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?
Reply 10
In the bouncing ball question n was the number of bounces right ^^.
Reply 11
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
Reply 12
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.
Reply 13
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.
Reply 14
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.
Reply 15
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 :frown:
Reply 16
Crossing out the correct answer and putting down the wrong answer is my worst nightmare............
Reply 17
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 :frown:


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.
Reply 18
integral of 1/1+x^4 anyone............ I got some long thing with ln and arctan in it, most likely wrong........
Reply 19
I asked one of the maths teacher in my school after and she couldn't do it....................

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