A figure skater spins with arms extended. When she pulls her arms in, what happe

Practice Questions

Q1
A figure skater spins with arms extended. When she pulls her arms in, what happens to her rotational speed?
  1. Increases
  2. Decreases
  3. Remains the same
  4. Becomes zero

Questions & Step-by-Step Solutions

A figure skater spins with arms extended. When she pulls her arms in, what happens to her rotational speed?
  • Step 1: Understand that the figure skater is spinning with her arms out. This is her starting position.
  • Step 2: Know that when she pulls her arms in, she changes her body shape while spinning.
  • Step 3: Recognize that pulling her arms in makes her moment of inertia smaller. Moment of inertia is a measure of how spread out her mass is.
  • Step 4: Remember the principle of angular momentum, which states that if no external forces act on a spinning object, its angular momentum stays the same.
  • Step 5: Since her moment of inertia decreases when she pulls her arms in, her rotational speed must increase to keep the angular momentum constant.
  • Angular Momentum Conservation – The principle that the total angular momentum of a closed system remains constant if no external torques act on it.
  • Moment of Inertia – A measure of an object's resistance to changes in its rotation, which depends on the mass distribution relative to the axis of rotation.
  • Rotational Speed – The rate at which an object rotates, often measured in revolutions per minute or radians per second.
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