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NTA Abhyas JEE Main2020PhysicsLaws of MotionPractice

The bob of a pendulum of mass m and length L is displaced 90 ° from the vertical and gently released. In order that the string may not break upon passing through the lowest point, its minimum strength must be

Options

  1. Am g
  2. B2   m g
  3. C3   m g
  4. D4   m g

Correct answer

C. 3   m g

Step-by-step solution

If v is velocity of the bob on reaching the lowest point, then 1 2 m v 2 = m g L To avoid breaking, strength of the string T L = m v 2 L + m g = 2 m g L L + m g = 3 m g

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