# Homework Help: Getting the avg angular vel.

1. Nov 10, 2007

### bigtymer8700

A flywheel with a radius of 0.300 starts from rest and accelerates with a constant angular acceleration of 0.600/s^2. i know how to solve for the atan but not for arad which is arad=w^2/r it ask Compute the magnitude of the tangential acceleration, the radial acceleration, and the resultant acceleration of a point on its rim at the start.

i know its 2pi=6.28rad all the way around and its acc. at .600rad/s^2 but i dont know where to go from there

Last edited: Nov 10, 2007
2. Nov 10, 2007

### Shooting Star

Your problem is not clearly formulated. Write clearly what is to be found out. Show your attempt.

Last edited: Nov 10, 2007
3. Nov 10, 2007

### bigtymer8700

it says at the start so would thetaf and thetai be both 0?

4. Nov 10, 2007

### Shooting Star

That means final theta = 2*pi.

w^2 = 0^2 + 2*a*(2pi). So, you know final w(omega).

Now find the linear speed, at the circumference.

Last edited: Nov 10, 2007
5. Nov 10, 2007

### bigtymer8700

so that means w^2=0^2 +2(.600)(6.283) it comes out to be w=2.86 but it says its wrong

6. Nov 10, 2007

### Shooting Star

As I said previously, your problem was not clearly formulated. How much time or what is the total angle?

7. Nov 10, 2007

### bigtymer8700

well if you use the w^2=Wo+2a(O-0o) its asking for the speed of the tip of the flywheel from the start so wouldnt the theta be 2xpi or just pi?

8. Nov 10, 2007

### aq1q

i agree with shooting star.. how long was it spun or what was its angular displacement?

9. Nov 10, 2007

### aq1q

and are u solving for the angular velocity or angular acceleration

By the way.. can u please explain what the units of atan and arad should be? it matters...
are atan and a rad angular acceleration or linear?

Last edited: Nov 10, 2007
10. Nov 10, 2007

### bigtymer8700

thats really where im stuck on i solved the other parts of the problem asking for the atan arad at 60degrees and 120degrees but what value would i use for the start theta? 360 or 180, 0?

11. Nov 10, 2007

### aq1q

well it starts at 0... (rest), also answer my previous post.. because thats essential... and while you are at it.. write down the problem exactly verbatim. and your attempt :D

12. Nov 10, 2007

### bigtymer8700

nvm yea you just use 0 for the start thanks guys

13. Nov 10, 2007

### aq1q

ok lol..

14. Nov 10, 2007

### Shooting Star

Hey bigtymer8700, you didn't put the D in the right place in your first post! Glad that you've understood.