# HL Math Paper 2- 24 Hours Later...

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1. How did you all find it? Let's share answers, people! :P
2. What did you get for the applications question? Writing an equation for v in terms of t?
3. (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)
4. 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 ^^.
5. For the ball bouncing did you guys use ar^n or ar^n-1 there was a bit debate in my school about it ^^.
6. 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.
7. (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? :/
8. (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.....
9. if you got v^2 you rearranged it wrong at the start :P.
10. (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?
11. In the bouncing ball question n was the number of bounces right ^^.
12. (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
13. (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.
14. 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.
15. (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.
16. (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
17. Crossing out the correct answer and putting down the wrong answer is my worst nightmare............
18. (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.
19. integral of 1/1+x^4 anyone............ I got some long thing with ln and arctan in it, most likely wrong........
20. I asked one of the maths teacher in my school after and she couldn't do it....................

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