## alexeis_nicole 2 years ago describe the motion of a point on a wheel that has a centre 4m off the ground, has radius of 15 cm, makes a full rotation every 10 seconds and starts at its highest point. use y=asink(t-b)+c model or cosine function.

1. Algebraic!

c=4 and a=.15 ... is that part clear?

2. alexeis_nicole

a=15 not .15..

3. Algebraic!

false. :) continuing... $f=\frac{ 1 }{10}$ $\omega = 2 \pi f$ $w= \frac{ \pi }{ 5 }$

4. Algebraic!

agree so far?

5. alexeis_nicole

yes i got that part

6. Algebraic!

so the phase...

7. Algebraic!

we want it to be at the highest point when t=0... sin =1 when theta = pi/2 pi/5 *(t-b) = pi/2 pi/5(-b) = pi/2 b= 5/2

8. Algebraic!

$y = .15 \sin (\frac{ \pi }{ 5} (t+\frac{ 5 }{2})) +4$

9. alexeis_nicole

would it be appropriate to keep(t-b) it at pi/5 *(t) + pi/2 ?

10. Algebraic!

you can... that's not the form they ask you to use though...

11. Algebraic!

whoops, should say b=-5/2 up there... typo

12. alexeis_nicole

oh okay. & also for cosine model it would just be $y=.15\cos(\frac{ \pi }{ 5 }t) +4$ right??

13. Algebraic!

yes

14. alexeis_nicole

why would it be -5/2 and not 5/2 ? :S

15. Algebraic!

why is b= -5/2? is that what you're asking?

16. alexeis_nicole

OH WAIT.. nvm.. you were referring to your reply before the equation. nvm. lol

17. alexeis_nicole

thanks!

18. Algebraic!

sure:)