Special Relativity - (Doug G7 Ch26 - Conceptual)

Which of the following are basic postulates of special relativity?

(There could be more than one correct choice.)

• A) Nothing can travel faster than the speed of light.

• B) No material object can be accelerated to the speed of light.

• C) The speed of light is the same for all observers.

• D) The laws of physics are the same in all reference frames.

• E) The laws of physics are the same in all inertial reference frames.

If you were in a spaceship traveling close to the speed of light with respect to Earth, you would notice that

• A) some of your physical dimensions were smaller than normal.

• B) your mass was less than normal.

• C) your mass was greater than normal.

• D) your pulse rate was greater than normal.

• E) none of the above effects occur.

You are riding in a spaceship that has no windows, radios, or other means for you to observe or measure what is outside. You wish to determine if the ship is stopped or moving at constant velocity. How can you do this?

• A) You can determine if the ship is moving by determining the apparent velocity of light in the spaceship.

• B) You can determine if the ship is moving by checking your precision time piece. If it's running slow, the ship is moving.

• C) You can determine if the ship is moving by lying down and measuring your height. If you are shorter than usual, the ship is moving.

• D) You should give up because you have taken on an impossible task!

One of Einstein's postulates in formulating the special theory of relativity was that the laws of physics are the same in reference frames that

• A) accelerate.

• B) move at constant velocity with respect to an inertial frame.

• C) oscillate.

• D) are stationary, but not in moving frames.

You are a passenger on a spaceship. As the speed of the spaceship increases, you will observe

• your watch slowing down.

• your watch speeding up.

• your watch losing time.

• your watch gaining time.

• nothing unusual about the behavior of your watch.

A spaceship traveling at constant velocity passes by Earth and later passes by Mars. In which frame of reference is the amount of time separating these two events the proper time?

• the Earth frame of reference

• the Mars frame of reference

• the spaceship frame of reference

• any inertial frame of reference

• any frame of reference, inertial or not

Observer A sees a pendulum oscillating back and forth in a relativistic rocket and measures its period to be t_A. Observer B moves along with the rocket and measures the period of the pendulum to be t_B. What is true about these two time measurements?

• t_A > t_B

• t_A = t_B

• t_A < t_B

• t_A could be greater or smaller than t_B depending on the direction of the motion.

A 30-year-old astronaut goes off on a long-term mission in a spacecraft that travels at speeds close to that of light. The mission lasts exactly 20 years as measured on Earth. Biologically speaking, at the end of the mission, the astronaut's age would be

• more than 50 years.

• exactly 50 years.

• less than 50 years.

• exactly 30 years.

• exactly 25 years.

Suppose one twin takes a ride in a spaceship traveling at a very high speed to a distant star and then back again, while the other twin remains on Earth. Compared to the twin who remained on Earth, the astronaut twin is

• younger than the Earth-twin.

• the same age as the Earth-twin.

• older than the Earth-twin.

• The ages cannot be determined from the information provided.

You are a passenger on a spaceship. As the speed of the spaceship increases, you will observe

• the length of your spaceship getting shorter.

• the length of your spaceship getting longer.

• the length of your spaceship is zero.

• no change in the length of your spaceship.