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NTA Abhyas JEE Main2020PhysicsLaws of MotionPractice

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

Options

  1. Ak ω 0 e - k t
  2. Bω 0 k e - k t
  3. Cω 0 k 1 - e - k t
  4. Dk ω 0 e - k t - 1

Correct answer

C. ω 0 k 1 - e - k t

Step-by-step solution

∵ ω = ω 0 - k ϕ or d ϕ d t = ω 0 - k ϕ Or ∫ 0 ϕ d ϕ ω 0 - k ϕ =   ∫ 0 t d t Or - 1 k   ln ω 0 - k ϕ 0 ϕ = t Or ln ω 0 - k ϕ ω 0 =   - k t ∴ ϕ = ω 0 k   1 - e - k t

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