Answer:
Frictional Force: Frictional force is the force caused by the relative motion of two surfaces that come into contact with each other.
Answer:
The magnitude of the angular acceleration is 
Explanation:
From the question we are told that
The angular speed of CD is 
time taken to decelerate is 
The final angular speed is 
The angular acceleration is mathematically represented as

substituting values


The negative sign show that the CD is decelerating but the magnitude is

5.4 x 1014Hz
wavelength x frequency = the speed of light