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Formative assessment questions for teaching physics

A2L Item 082

  • Description: What is the maximum angular velocity that allows a bug to remain fixed on a rotating disk.
  • Goal: Problem solving
  • Source: UMPERG
  • Keywords: Dynamics, Friction, Mechanics, Rotational Motion

The question for students:

Item082_fig1.gif

A bug sits on a disk at a point 0.5 m from the center. If the coefficient of friction between the bug and disk is 0.8, the maximum angular velocity the disk can have before the bug slips off the disk is most nearly:

  1. 2 rad/s
  2. 4 rad/s
  3. 5.2 rad/s
  4. 16 rad/s
  5. None of the above
  6. Cannot be determined

Commentary for teachers:

Answer

(2) Some students may respond (6) thinking that the mass of the bug is needed for solution.