Creative Commons License Copyright © Michael Richmond. This work is licensed under a Creative Commons License.

Stop the Earth!

Fred's life is too complicated. "I can't keep up with it all!" he cries. "I must slow things down ... I know -- I'll stop the Earth from rotating!"

Fred grabs a giant steel girder, hops into space, and jams the girder hard against the surface of the Earth at the equator. The incredible grinding, scraping friction provides a steady friction force of F = 1 billion Newtons against the ground.

  1. What is the moment of inertia of the Earth?
  2. What is the initial angular velocity of the Earth? (a vector)
  3. What is the friction force Fred is applying to the Earth? (a vector)
  4. What is the torque Fred is applying to the Earth? (a vector)
  5. What is the angular acceleration of the Earth? (a vector)
  6. Assuming that Fred can maintain this same force for a long time, how long will it take him to halt the Earth's rotation?

    7. (if you have time)

  7. How long has the Earth been in existence?
  8. How long will the Sun continue to shine?

Creative Commons License Copyright © Michael Richmond. This work is licensed under a Creative Commons License.