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JEE Main202126 Feb 2021Evening ShiftPhysicsLaws of MotionActual

An inclined plane making an angle of 30 ° with the horizontal is placed in a uniform horizontal electric field 200 N C as shown in the figure. A body of mass 1 kg and charge 5 mC is allowed to slide down from rest at a height of 1 m . If the coefficient of friction is 0 . 2 , find the time taken by the body to reach the bottom. g = 9 . 8 m s - 2 ; sin 30 ° = 1 2 ; cos 30 ° = 3 2

Options

  1. A0 . 92   s
  2. B1 . 3   s
  3. C0 . 46   s
  4. D2 . 3   s

Correct answer

B. 1 . 3   s

Step-by-step solution

here N = 9 . 8 cos 30 + 1 sin 30 ≈ 9   N so a = 9 . 8 sin 30 - 1 cos 30 - μ N 1 a = 2 . 233   m   s - 2 By S = u t + 1 2 a t 2 = 1 2 2 . 233 t 2 sin 30 ° t ≈ 1 . 3   sec

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