Thinking about it
In Length and Time
Transformations
Four-Momentum
Kawakami Trivia
100

Matt and Professor Kawakami buy a spaceship with the funds from their startup. Matt goes for a ride with his treasured watch at .5c while Professor Kawakami sits in his office for K-Drama hour, along with his favorite clock. From the professor's point of view, which clock ticks slower?

What is the moving clock?

100

How one converts velocity into special relativity units

What is dividing by c?

100

The formula for calculating length contraction

What is L = LR/γ ?

100

Multiply by this to convert the matrix:

[m; mvx; mvy; mvz

into four-momentum:

[pt; px; py; pz]

What is γ ( or 1/√(1-β2))

100

What does Professor Kawakami have a Ph.D. in?

What is Physics?

200

The time measured in the reference frame which also does not observe movement, often notated as Δ𝜏

What is proper time?

200

(Bring up graph)

Which event happens first in each frame? 

In ground frame: A occurs first

In moving frame: They are simultaneous

200

The Lorentz transformation for x in a moving frame

What is x' = γ(x - βt)?

200

A particle has a four-momentum of:

[10 kg; 3 kg; 4 kg; 0 kg]

What is its mass?

What is 8.12 kg?
200

Professor Kawakami's office's location

What is the Physics Research Building, room 2030?

300
The notation for the velocity of a moving frame

What is β?

300

Sonic sees a chili dog stand and runs to it at a speed very close to that of light. Tails, observing Sonic, measures Sonic to have been moving for 5 seconds across a distance of 4 seconds. Sonic claims he was moving for 3 seconds. Set up how to find how far Sonic travelled using spacetime interval.

What is 52 - 42 = 32 - (Δx)2?

300

Professor Kawakami is riding a train to Matt. The train is moving at a velocity of .75. According to the professor, the trip takes 60 seconds. How long did the trip take, according to Matt?

What is 90.7 seconds?

300

A particle has a four-momentum of:

[9 kg; 3 kg; 0 kg; 0 kg;]

What is its velocity?

What is .3?

300

What is the number in Professor Kawakami's email?

What is 15?
400

You're sitting on your couch watching TV when your cat zooms by at a high speed relative to that of light. You notice that your cat's length looks different to you, even though it doesn't seem to have noticed a change itself. How has your cat's length changed from your perspective? 

The cat's length appears shorter

400

Matt is riding a train to Professor Kawakami. The train is moving at .6 relative to the ground. According to the professor, who is waiting at the station, Matt's trip took 90 seconds. How long does Matt say the trip took?

What is 72 seconds?

400

A train is moving at a velocity of .5. An observer on the train notes that two firecrackers 50 microseconds apart explode simultaneously. According to an observer on the ground, how much time passed between these explosions? (Round to the nearest whole number)

What is 26 microseconds?

400

A particle has a mass of 5 kg and a velocity of .7. What is the four-momentum of the particle according to an observer moving at .6?

What is [6.25; 4.375; 0; 0]

400

The place where Professor Kawakami got his Ph.D.

What is the University of California?

500

Spatial coordinates (x, y, z) with synchronized clocks that record events instantaneously

What is a reference frame?

500

A train in SPAAAAACE travels between stations that are about 4.6 hours apart at a constant velocity. The trip takes 8.4 hours, according to an impatient commuter waiting at a station. How long was the trip according to a passenger?

What is 7 hours?

500

N and V are robots that are capable of moving at speeds comparable to that of light. Both are racing a distance of 6000 km across the planet's surface in the +x direction. N has a constant speed of .6 and V has a constant speed of .8. How much does V win the race by?

What is ~.008 seconds?

500

A blob with a mass m travelling with an x-velocity of .8 (as measured by the ground frame) collides with another blob with a four-momentum of

[.25m; -.25m; 0; 0]

The blobs combine when they collide. What is the final mass in terms of m?

What is 1.59m?

500

The top three reviews on ratemyprofessor.com describe him as this phrase.

What is "totally legit"?