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NEETPhysicsLaws of Motion

Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): For a block on a rough horizontal surface pulled by a hanging mass via a string and pulley, if the horizontal surface is made completely smooth, the tension in the connecting string will decrease. Reason (R): Removing friction increases the acceleration of the system, and for the hanging mass, the

Options

  1. ABoth (A) and (R) are correct but (R) is not the correct explanation of (A)
  2. BBoth (A) and (R) are correct and (R) is the correct explanation of (A)
  3. C(A) is correct but (R) is not correct
  4. D(A) is not correct but (R) is correct

Correct answer

B. Both (A) and (R) are correct and (R) is the correct explanation of (A)

Step-by-step solution

Let the mass of the block on the surface be m₁ and the hanging mass be m₂ . The equation of motion for the hanging mass is: m₂ g - T = m₂ a Rearranging this gives the tension in the string: T = m₂(g - a) When the horizontal surface is rough, there is an opposing frictional force f_k , and the acceleration is a = m₂ g - f_k m₁ + m₂ . When the surface is made completely smooth, the opposing friction f_k becomes zero. The net driving force on the system increases, which causes the acceleration a of the system to incre

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