Compact disk angular acceleration

[jkhays]

Homework Statement

A compact disc speeds from rest to 5200 rpms in 620 rad. Diameter is 5.0cm
-how many revolutions did it make in this time
-what is the angular acceleration in rad/s^2
-how long does ti take to reach this speed

Homework Equations

The Attempt at a Solution

i was able to find the first part by
620(180/π) = 35523 dividing that by 360 and getting 99 revolutions

for the last 2, i am completely lost to where i even begin solving them.thank you..

 

[tiny-tim]

welcome to pf!

hi jkhays! welcome to pf!

you can use the usual constant acceleration equations, with angular acceleration velocity and displacement instead of ordinary (linear) acceleration velocity and displacement

 

[climb515c]

You know ω initial and ω final, and Δθ. You can solve for angular acceleration using one of the kinematics equations for constant acceleration. Once you have alpha you can solve for t.