標題:
Physics( angular velocity )
發問:
Two friction disks A and B are both rotating freely at 240 rpm counterclockwise when they are brought into contact. After 8 s of slippage, during which each disk has a constant angular acceleration, disk A reaches a final angular velocity of 60 rpm counterclockwise. Determine (a) the angular acceleration of each... 顯示更多 Two friction disks A and B are both rotating freely at 240 rpm counterclockwise when they are brought into contact. After 8 s of slippage, during which each disk has a constant angular acceleration, disk A reaches a final angular velocity of 60 rpm counterclockwise. Determine (a) the angular acceleration of each disk during the period of slippage, (b) the time at the angular velocity of disk B is equal to zero.
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最佳解答:
(a) Use: impulse = change of angular momentum T.(8) = I.(60 - 240).(2.pi/60) where T is the torque applied to disk A I is the moment of inertia of disk A pi = 3.14159... hence, T/I = [(60 - 240).(2.pi/60)]/8 but T/I = angular acceleration i.e. angular acceleration = [(60 - 240).(2.pi/60)]/8 = -2.356 rad/s^2 (b) The final angular velocity of 60 rpm in the clockwise direction, hence angular acceleration of disk B = [(-60 - 240).(2.pi/60)]/8 rad/s^2 = - 3.927 rad/s^2 Use equation of motion: v = u + at with v = 0 rad/s, u = 240 x 2.pi/60 rad/s =25.133 rad/s, a = -3.927 rad/s^2 hence, 0 = 25.133 + (-3.927)t t = 6.4 s
其他解答:
For disk A's angular acceleration, I have no problem with it, but the probelm did not say the final angular velocity of disk B is equal to disk A's, so I think the answer for disk B's angular accleration isn't right.
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