Seniors HL Relativity

We do not usually observe relativistic effects in our daily lives because 

• we are moving at speeds much less than c. 
• we are much larger than atoms. 
• we are much heavier than elementary particles. 
• we are much lighter than stars. 

If you travel at the speed of light a second can be observed to last forever.

• True
• False

There are two clocks one is stationary on the earth the other is traveling close to the speed of light around the earth. If we put the clocks back together after the second clock makes it back from its trip, the times are compared. What do you expect to occur?

• More time elapsed on the stationary clock

• More time elapsed on the traveling clock

• No time has changed between them

One of the most startling consequences of time dilation is that a moving clock ______________ relative to a stationary observer.

• Speeds up
• Slows down

The relativistic expression for length contraction of an object moving at velocity v is

• $L=L_0\sqrt{1-\frac{v^2}{c^2}}$

• $L=\frac{L_0}{\sqrt{1-\frac{v^2}{c^2}}}$
  

• $L\ =\ L_0\sqrt{1-\frac{c^2}{v^2}}$
  

• $L=\frac{L_0}{\sqrt{1-\frac{c^2}{v^2}}}$
  

A particle with a lifetime of 2.0 × 10^–6 s moves through the laboratory with a speed of 0.9 c. Its lifetime, as measured by an observer in the laboratory, is

• 2.0 × 10^–6 s
• 3.2 × 10^–6 s
• 4.6 × 10^–6 s
• 5.4 × 10^–6 s
• 6.3 × 106–6 s

A train has a rest length of 100 m. Traveling at a very high velocity, it goes through a tunnel of length 80 m. Observers located at both ends of the tunnel note that at one instant the train appears to exactly fit within the tunnel.

What is the velocity of the train expressed in units of c?

• 0.333 c

• 0.50 c

• 0.60 c

• 0.80 c

• 0.866c

How fast does a rocket have to move relative to an observer for its length to be contracted to 95% of its original length?

• 0.2 c
• 0.3 c
• 0.4 c
• 0.5 c

A Klingon spaceship is approaching Earth at approximately 0.8 c measured relative to Earth. The spaceship directs a laser beam forward directly through your physics classroom window.

You measure the speed of this light to be:

• 1.8 c

• 1.0 c

• 0.9 c

• 0.8 c

• 0.2 c

What does the relativity of simultaneity say?

• Two events may occur at the same time in one reference frame, but not another.
• If two events occur at the same time in one reference frame, they will occur at the same time in all reference frames.