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NEETPhysicsLaws of Motion

Assertion : A body of mass 10 kg is placed on a rough inclined surface (( =07) ). The surface is inclined to horizontal at angle (30^ ). Acceleration of the body down the plane will be zero. Reason : Work done by friction is always negative.

Options

  1. AIf both Assertion and Reason are correct and Reason is the correct explanation of Assertion
  2. BIf both Assertion and Reason are true but Reason is not the correct explanation of Assertion
  3. CIf Assertion is true but Reason is false
  4. DIf Assertion is false but Reason is true

Correct answer

C. If Assertion is true but Reason is false

Step-by-step solution

Quick justification: the weight component down the plane (49 N) is less than maximum friction ( ( 59.4 ~N )), so the body doesn't move ( ) acceleration (=0 ) (Assertion true). The Reason is false because friction's work isn't always negative - the sign depends on the direction of displacement relative to the friction force (static friction can even do positive work in some cases).

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