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Angular acceleration and angular velocity

by John78
Tags: acceleration, angular, velocity
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John78
#1
Mar15-12, 07:44 PM
P: 21
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
360/57.3=6.28 rad/s
6.28/6= 2.09 rad/sec

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.
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emailanmol
#2
Mar15-12, 07:57 PM
P: 297
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
John78
#3
Mar16-12, 06:14 AM
P: 21
angular acceleration = 0


what about angular velocity?

tiny-tim
#4
Mar16-12, 07:14 AM
Sci Advisor
HW Helper
Thanks
tiny-tim's Avatar
P: 26,160
Angular acceleration and angular velocity

Hi John78!
Quote Quote by John78 View Post
angular acceleration = 0
Correct.
what about angular velocity?
Your formula
Angular velocity= angular displacement/time
is fine


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