Homework 15 Due Friday, April 30, 2004

  1. A person riding on the roof of a freight-train car fires a gun pointed forward. Compare the velocity of the bullet with respect to the ground when the train is at rest to that when the train is moving.

  2. Suppose, instead, that the person riding on top of the frieght car shines a searchlight beam in the direction in which the train is traveling. Does the light beam travel faster with respect to the ground than it would is she had shone it while standing at rest on the ground? Explain.

  3. If you were in a rocket ship traveling away from the earth at a speed close to the speed of light, what changes would you note in your pulse? Explain.

  4. If you were on earth monitoring a person in a rocket ship traveling away from the earth at a speed close to the speed of light, what changes would you note in his pulse? Explain.

  5. Sally flies past Martin in her spaceship at nearly the speed of light. According to Martin, Sally's clock runs slow. According to Sally, does Martin's clock run slow, fast, or at the normal rate? Explain.

  6. In relativity we find that "moving clocks run slow," but this effect does not occur because the motion alters the way a clock works. Why does it occur? What does it mean to say that "moving clocks run slow"?