Homework Help: Angular acceleration and angular velocity

1. Mar 15, 2012

John78

1. The problem statement, all variables and given/known data

Calculate the angular acceleration and angular velocity of a 4 kg object rotating in a circle of 3 m radius in a time of 6 s.

2. Relevant equations

3. The attempt at a solution

Angular acceleration = ω2*r

C=2∏r= 2*3.14*3=18.84

Angular acceleration= (2.09)2*3=12.54???????

Angular velocity= angular displacement/time ????

I just want to check whether my working is correct or not.

2. Mar 15, 2012

emailanmol

Nope.Its not right.

Remember, angular acceleration is dw/dt.

The acceleration w^2*r is centripetal accelwration.

Infact writing angular acceleration as w^2*r is dimemsionally inconsistent.

As nothing had been told about how w changes with time nothing can be said about angular acceleration.

In such cases w is assumed to be constant making angular acceleration 0

3. Mar 16, 2012

John78

angular acceleration = 0

what about angular velocity?

4. Mar 16, 2012

Hi John78!
Correct.