Learning objective


A law enforcement officer in an intergalactic "police car" turns of a red flashing light and sees it generate a flash every 1.5s. A person on the earth measures that the time between flashes is 2.5s. How fast is the "police car" moving relative to the earth?

Suppose that you are traveling on board a spacecraft that is moving with respect to the earth at a speed of 0.975c. You are breathing at a rate of 8.0 breaths per minute. As monitored on earth, what is your breathing rate?

An astronaut travels at a speed of 7800m/s relative to the earth, a speed that is very small compared to c. According to a clock on the earth, the trip lasts 15 days. Determine the difference (in seconds) between the time recorded by the earth clock and the astronaut's clock. [Hint: When v" c, the following approximation is valid:
 γ = 1-½(v²/c²)]

As observed on earth, a certain type of bacteria is known to double in number every 24.0 hours. Two cultures of these bacteria are prepared, each consisting initially one bacterium. One culture is left of earth and the other placed on a rocket that travels at a speed of 0.866c relative to the earth. At a time when the earthbound culture has grown to 256 bacteria, how many bacteria are in the culture on the rocket, according to an earth-based observer?