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 force of F = 1 billion Newtons against the ground.

  1. How much torque is Fred applying to the Earth?
  2. What is the moment of inertia of the Earth? Use these values: mass of Earth M = 5.98 x 1024 kg and radius of Earth R = 6.37 x 106 m.
  3. What is the current angular velocity of the Earth?
  4. Assuming that Fred can maintain this same force for a long time, how long will it take him to halt the Earth's rotation?

    5. (if you have time)

  5. How long has the Earth been in existence?
  6. How long will the Sun continue to shine?

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