A Bluray disc is 12 cm in diameter. When put into a player, it takes 30 seconds

Question

A Bluray disc is 12 cm in diameter. When put into a player, it takes 30 seconds for the disc to
accelerate to its playing speed of 1500 revolutions per minute.
(a) Find the number of revolutions the disc makes during the time it takes to reach its playing
speed.
(b) If a movie is 2 hours long, how far will a point on the edge of the disc travel during the movie.
You may ignore the distance travelled while the disc is reaching its playing speed.
(c) Make plots of ?, ? and ? for the first 1 minute after the disc is put in the player. You may
assume the disc spins counterclockwise.

Please explain using equations..I'm having a hard time with which equation to use for which variable.

Explanation / Answer

a) wf = 1500 x 2pi rad/ 60 sec = 157.08 rad/s

alpha = wf - 0 / t = 5.24 rad/s2

wf^2 - wi^2 =2 x alpja x angle

angle = (157.08^2 - 0 ) / 2x5.24 = 2354.40 rad

angle / 2pi = 374.72 rev

b) angle = alpha xt^2 /2   = 5.24 x (2 x 3600)^2 /2

distance = r x angle = 0.06 x 5.24 x (2 x 3600)^2 /2   = 8149248 m

c)

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