A ceiling fan is rotating at 0.50 rev/s. When turned off, it slows uniformly to a stop in 11 s.

Question

(a) How many revolutions does it make in this time?

(b) Using the result from part (a), find the number of revolutions the fan must make for its speed to decrease from 0.50 rev/s to 0.25 rev/s.

Answer 1

Wo = 0.5rev/s
Wf = 0.25rev/s
t = 11s
Revolution = ?

a) Acceleration = 0.5rev/s / 11s
Acceleration = -0.045rad/s²

Θ = Wot + 1/2(-a)t
Θ = 0.5rev/s(11s) - 1/2(0.045rad/s²)(11²)
Θ = 2.75rev <-- Answer

b) Average speed = (0.5rev/s + 0.25rev/s) / 2
Average speed = 0.375rev/s

Θ = Vav * t / 2
Θ = 0.375rev/s * 11s / 2
Θ = 2.06rev <-- Answer

Answer 2

3. A pulley of radius 0.5m, on a motor is turning at 30 Rev/s and slows down uniformly in 2.0s. Calculate;
a. The angular acceleration of the motor.
b. The number of revolutions it makes in this time.
c. The length of the belt it winds in this time

Answer 3

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Answer 4

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