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NTA Abhyas JEE Main2020PhysicsRotational MotionPractice

A solid cylinder is given a velocity v 0 and an angular speed ω 0 in the anticlockwise direction and then it is placed gently on a very long rough plank (initially at rest) as shown in the figure. Then, choose the incorrect statement:

Options

  1. Athe friction force on the disc is in the backward direction till pure rolling starts
  2. Bthe friction force between the disc and the plank is kinetic in nature till pure rolling starts
  3. Cthe total momentum of system (disc and plank) is conserved
  4. Dthe angular momentum of the disc about any point on the horizontal surface remains conserved

Correct answer

D. the angular momentum of the disc about any point on the horizontal surface remains conserved

Step-by-step solution

Initial velocity of point of contact of disc is in forward direction. Hence friction is in backward direction and kinetic in nature. Net force on the system is zero. So momentum is conserved.

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