Relativity Part 2

Relative to a stationary observer, a moving object

• appears shorter than normal.

• appears longer than normal.

• keeps its same length time.

• can do any of the above. It depends on the relative velocity between the observer and the

  object.

An object moves in a direction parallel to its length with a velocity that approaches the velocity of light. The width of this object, as measured by a stationary observer,

• approaches infinity.

• approaches zero.

• increases slightly.

• does not change.

An object moves in a direction parallel to its length with a velocity that approaches the velocity of light. The length of this object, as measured by a stationary observer,

• approaches infinity.

• approaches zero.

• increases slightly.

• does not change.

How fast would a rocket ship have to move to contract to half of its proper length (as observed by a stationary object)?

• 0.50c

• 0.65c

• 0.78c

• 0.87c

The length of a spaceship is 10 m when it is at rest. If the spaceship travels by you with a speed of 0.70c, what length does it appear to you?

• 5.5 m

• 7.1 m

• 12 m

• 18 m

The closest star to our solar system is Alpha Centauri, which is 4.30 light years away. A spaceship with a constant speed of 0.800c relative to the Earth travels toward the star. What distance does the space ship travel according to a passenger on the ship?

• 2.58 ly

• 3.52 ly

• 4.12 ly

• 4.30 ly

True or False. Because of time dilation, observers moving at a constant velocity relative to each other measure different time intervals between two events.

True or False. A length measured in the frame in which the body is at rest (the rest frame of the body) is called a proper length.

Modified True or False. Write True if the statement is true. Otherwise, change the underlined word.

In a reference frame in which the object is moving, the measured

length parallel to the direction of motion is longer than its proper length.

Modified True or False. Write True if the statement is true. Otherwise, change the underlined word.

It is important to note that this length contraction occurs only along the direction of the motion.