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A solid body rotates about a stationary axis so that its angular velocity  depends on the rotational angle `phi` as `omega = omega_0 - k phi` where `omega_0` and k are positive constants . At the moment  t = 0,  `phi ` = 0. Find the time dependence of rotation angle :


Options:
A .  `k omega_0 e^-(kt)`
B .  ` omega_0/K e^-(kt)`
C .  `omega_0/K (1 - e^-(kt))`
D .  `k/omega_0 (e^-(kt) - 1)`
Answer: Option C

`because`    ` omega = omega_0 - k phi`

or ` (d phi)/(dt) = omega_0 - k phi`

or `int_0^phi (d phi)/(omega_0 - k phi)` = `int_0^1 dt`

or `- 1/k [In (omega_0 - k phi)]_0^phi` = t

or `In ((omega_0 - k phi)/(omega_0) = - kt`

`:.`           `   phi = omega_0/k  (1 - e^-(kt))`




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