Review Questions

1. A pilot of a spaceship traveling at 90% the speed of light (0.9c) turns on the ship’s laser headlights just as it passes a stationary observer. Which of the following statements is true?

   1. The pilot will measure the speed of the light coming out of the headlights as c, and the observer will measure the speed of the light as 0.9c.
   2. The pilot will measure the speed of the light coming out of the headlights as c, and the observer will measure the speed of the light as 1.9c.
   3. The pilot will measure the speed of the light coming out of the headlights as 0.9c, and the observer will measure the speed of the light as 1.9c.
   4. The pilot will measure the speed of the light coming out of the headlights as 1.9c, and the observer will measure the speed of the light as 0.9c.
   5. The pilot will measure the speed of the light coming out of the headlights as c, and the observer will measure the speed of the light as c.

2. Which of the following graphs best represents the length L of a horizontal meter stick traveling horizontally with speed v as it approaches the speed of light?

   1. 

   2. 

   3. 

   4. 

   5. 

3. Two identical, very precise clocks are started at the same time. One clock is taken on a trip at a very high speed, and the other is left at rest on Earth. When the traveling clock is returned to Earth, it shows that one hour has passed. Which of the following could be the time that has passed on the Earth-bound clock?

   1. 30 minutes
   2. 45 minutes
   3. 59 minutes
   4. 1 hour
   5. 2 hours

4. The mass of an object increases as its speed increases. This increase in mass comes from

   1. nuclear binding energy.
   2. electron energy in the ground state.
   3. potential energy being converted into mass by E = mc².
   4. kinetic energy being converted into mass by E = mc².
   5. the lower pressure on the mass.