Acertain cd has a playing time of 76 minutes. when the music starts, the cd is rotating at an angular speed of 4.10 × 10 2 4.10×102 revolutions per minute (rpm). at the end of the music, the cd is rotating at 2.90 × 10 2 2.90×102 rpm. find the magnitude of the average angular acceleration of the cd. express your answer in rad/s².

average acceleration =   2.74 x 10⁻³ rad/s²

Explanation:

given,

CD playing time = 76 minutes

initial angular speed of CD = 4.10 × 10² rev/min

                                             =

                                             = 42.9 rad/s

final angular speed of CD = 2.90 × 10² rev/min

                                           =

                                           = 30.37 rad/s

average acceleration =

                                   =  

average acceleration =  0.00274 rad/s²

average acceleration =  2.74 x 10⁻³ rad/s²

speed of light in vacuum is 300,000 km/s

speed of light in other mediums is given by the expression v = c/n, where c is the speed of light in vacuum and n is the refractive index of medium.

for the first medium v = 200,000 km/s

  so, refractive index of medium = 300000/200000 = 1.5

    1.5 refractive index is usually for glass. so first medium is glass.

for the second medium v = 250,00 km/s

so, refractive index of medium = 300000/250000 = 1.2

    1.2 refractive index is usually for water. so second medium is water.

for the third medium v = 0 km/s

so, refractive index of medium = 300000/0 = ∞

    ∞ refractive index is usually for opaque mediums. so third medium is opaque medium.