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NTA Abhyas JEE Main2020PhysicsLaws of MotionPractice

A ceiling fan rotates about its own axis with some angular velocity. When the fan is switched off, the angular velocity becomes 1 4 t h of the original in time t and n revolutions are made in that time. The number of revolution made by the fan during the time interval between switch off and rest are (Angular retardation is uniform)

Options

  1. A4 n 15
  2. B8 n 15
  3. C16 n 15
  4. D32 n 15

Correct answer

C. 16 n 15

Step-by-step solution

ω 4 2 = ω 2 - 2 α n ( 2 π ) ∴ 2 α n 2 π = ω 2 - ω 2 16 ∴ 2 π n = 15 16 ω 2 2 α 0 = ω 2 - 2 α n ′ ∴ 2 π n ′ = ω 2 2 α ∴ n ′ = 16 15 n

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