.Given:
The radius of the disk is,

The angular speed is

(a)
the linear speed at a point on the outer rim is,

Hence the linear speed is 2.07 m/s.
(b)
The centripetal acceleration is,

Hence the acceleration is 71.4 m/s^2.
(c)
The linear speed at halfway between the center and the outer rim is

The centripetal acceleration is,

Hence the linear speed is 1.04 m/s, and the centripetal acceleration is 36.0 m/s^2.