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Mathematics 9 Online
OpenStudy (anonymous):

a particle is moving with acceleration s''(t)=t-2 at time t=0, s(0)=0 and the velocity s'(0)=5. find the position function s (t) at time t

OpenStudy (anonymous):

I have to hand this in REALLY soon and I really need help with this problem!

OpenStudy (isaiah.feynman):

integrate the acceleration function TWO times!!!

OpenStudy (anonymous):

t-2 function?

OpenStudy (isaiah.feynman):

Yes!!!

OpenStudy (anonymous):

ok how?

OpenStudy (anonymous):

do i find the antiderivative of it twice?

OpenStudy (isaiah.feynman):

Using integration. If you wanna know more you can message me but since its urgent the solution is... First integration gives you 1/2t^2-2t. Integrating again for the second time gives you 1/6t^3-t^2. That's the position function! If you differentiated it twice you will get t-2 again.

OpenStudy (anonymous):

thanks but I kinda need to know the steps too!

OpenStudy (anonymous):

i'm not completely understanding integration either..

OpenStudy (isaiah.feynman):

Okay there are nearly 200 formulas for integration but to solve your problem I used one of the basic rules... \[\int\limits_{?}^{?} x^{n}dx = \frac{ 1 }{ n+1 } x^{n+1} \] .

OpenStudy (anonymous):

ok~

OpenStudy (isaiah.feynman):

Understood?

OpenStudy (anonymous):

yes... but do you mind explaining alil more?

OpenStudy (anonymous):

so whats the n?

OpenStudy (isaiah.feynman):

n is any arbitrary power

OpenStudy (anonymous):

ok~ so how does the t-2 fit in the equation?

OpenStudy (isaiah.feynman):

Oh okay its a long answer to type!!! I wish I could use skype to show you.

OpenStudy (anonymous):

haha me too. can you explain it at all?? :(

OpenStudy (isaiah.feynman):

Okay first in integration we assume t and -2 are two functions, when you want to integrate two functions such as t-2 its the integral of t minus the integral of 2. So to integrate t itself I used the formula I showed you earlier where n is 1 in this case. The integral of 2 is 2t. So if you follow that you will get the first integral of that acceleration and if you follow the same procedure you will get the second integral which is the position function!!!

OpenStudy (anonymous):

1/2 t^2 came from the formula?

OpenStudy (isaiah.feynman):

Yes!!!

OpenStudy (anonymous):

ok so what does s'(0) =0 and s'(0)=5 have to do with this problem?

OpenStudy (anonymous):

and what is n to find the second equation? how do I know ?

OpenStudy (isaiah.feynman):

To your first question the answer is nothing! To your second question n is 2!

OpenStudy (anonymous):

then why is it 1/6?

OpenStudy (isaiah.feynman):

I told you n is any arbitrary power/exponent. 2 is an exponent on t... 1/6 is a coefficient of t

OpenStudy (anonymous):

right but how can i get 1/6? isn't it 1/3 x^3 when I plug 2 in for n?

OpenStudy (isaiah.feynman):

I wish i could attach a video!

OpenStudy (anonymous):

lol

OpenStudy (anonymous):

sorry I'm not getting this.. oh well i gotta hand it in soon now...

OpenStudy (isaiah.feynman):

Will your teacher ask how you got your answer?

OpenStudy (anonymous):

yeah

OpenStudy (isaiah.feynman):

I guess its too late for me to do some more explanation.

OpenStudy (anonymous):

haha you helped me alot. thanks

OpenStudy (isaiah.feynman):

Np

OpenStudy (isaiah.feynman):

Hey

OpenStudy (anonymous):

yup?

OpenStudy (isaiah.feynman):

Did it go smoothly?

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