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NTA Abhyas JEE Main2020PhysicsLaws of MotionPractice

Three blocks A , B and C of equal mass m are placed one over the other on a smooth horizontal ground as shown in the figure. Coefficient of friction between any two blocks is 0 . 5 . The maximum value of the mass of block D so that the blocks A , B and C move without slipping over each other is

Options

  1. A6 m
  2. B5 m
  3. C3 m
  4. D4 m

Correct answer

C. 3 m

Step-by-step solution

Blocks A and C both move due to friction. But less friction is available to A as compared to C because the normal reaction between A and B is less. Maximum friction between A and B can be f m a x = μ m A g = 1 2 m g ∴ Maximum acceleration of A can be a m a x = f m a x m = g 2 Further a m a x = m D g 3 m + m D Or g 2 = m D g 3 m + m D Or m D = 3 m

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