Question

A disk of radius 12 cm, initially at rest, begins rotating about its axis with a constant angular acceleration of 7.8 rad/s2. What are the following values at t = 4.0 s?

(a) the angular velocity of the disk

(b) the tangential acceleration at and the centripetal acceleration ac of a point at the edge of the disk
at =
ac =

Answer 1

I don't know how to find ac, but I can help you with at and angular velocity of the disk.

(a) (7.8 rad/s^2)/4.0s = 31.2=angular velocity

at=7.8*.12=0.936

Answer 2

Tangential acceleration is the instantaneous linear acceleration associated with the particle at distance (r) from the center of rotation.
thus
Centripetal Accel= (angular accel)(r)

Answer 3

ac = (omega^2)*(radius)
= (31.2^2)*(0.12 m)
= 116.8