What is the magnitude of its average angular acceleration in rad/s^2 of the wheel?

Question

A flywheel rotating at 12 rev/s is brought to rest in 6 s.

Answer 1

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By:-
omega(final) = omega(initial) + alfa x time
=>0 = 12 + alfa x 6
=>alfa = -12/6 = -2 rad/sec^2 [-ve showing that, it is retardation which is acting against the angular velocity (omega) to stop the wheel.]

Answer 2

ave angular acceleration = change in angular velocity / change in time
= -12rev/s / 6s
= -2rev/s^2
but you need to convert it to rad/s^2:
1rev = 2pi rad
-2rev/s^2 * 2pi rad/1rev = -4pi rad/s^2

Answer 3

Simply
α = ω/t (ω----->angular velocity α------->angular acceleration)
α = 12x2π/6
= 4π rad/sec^2