Questions 12.) and 13.) pertain to the following scenario: A computer hard disk
ID: 1601001 • Letter: Q
Question
Questions 12.) and 13.) pertain to the following scenario: A computer hard disk is initially at rest when the power is turned on and it begins accelerating at 200.0rad/s^2. The disk accelerates until reaching an angular speed of exactly 6000rpm, then continues rotating at constant angular speed. How long does it take for the disk to reach an angular speed of 6000rpm? a.) pi seconds b.) 2 pi seconds c.) 3 pi seconds d.) 4 pi seconds e.) none of these How many revolutions has the disk made one (1) minute after the power is turned on? a.) 5843 revolutions b.) 3116 revolutions c.) 2479 revolutions d.) 1117 revolutions e.) none of theseExplanation / Answer
Given angular acceleration alpha = 200 rad/s
initial angular velocity omega1 = 0
final omega2 = 600 rpm = 600 * 2pi / 60
omega2 = 20 pi rad/s
from
omega2 = omega1 + (alpha * t)
20 * pi = 0 + ( 200 * t)
t = pi / 10 s
Answer si e) none of the above
13)
theta = (omega1 * t) + (1/2 * alpha * t^2)
theta = 0 + 1/2 * 200 * (pi/10)^2
theta = 9.869 rad
theta = 9.869 * 360 / 2pi
theta = 5580.78 rev
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