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When a celling fan is switched off, its angualr velocity falls to half while it makes `36` rotations. How many more rotations will it make before coming to rest ?A. `24`B. `36`C. `18`D. `12` |
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Answer» Correct Answer - D Here `theta = 36 xx 2pi, omega = (omega_(0))/(2)` As `omega^(2) = omega_(0)^(2) = 2 alpha theta`, `((omega_(0))/(2))^(2) - omega_(0)^(2) = 2 alpha (36 xx 2pi)` `- (3omega_(0)^(2))/(4) = 144pi alpha or alpha = - (omega_(0)^(2))/(192 pi)` Again. form `2 alpha theta = omega^(2) - omega_(0)^(2)`, As finally fan will stop, So `omega = 0` and `omega_(0)//2 =` Initialy angular velocity `2 (-(omega_(0)^(2))/(192pi)theta) = 0 - ((omega_(0)^(2))/(2)), theta = 24 pi` Let no. be rotations be `n` `:. 24 pi = 2pi n or n = 12` |
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