Pop Quiz

A few guys were studying in our dorm the other day, and somehow the following question came up:

Which of the following has more kinetic energy?

(a) A fully loaded freight train traveling at 79 mph across country
(b) The shuttle orbiting at mach 25

The answer wasn't immediately obvious. We started geeking out about it, looking stuff up online and doing some calculations. Some predicted the train, others predicted the shuttle.

The answer?

A typical freight train weighs about 8,000 tons. It has a kinetic energy of 4,767,000,000J.
The Shuttle Orbiter has a mass of 99,318 kg. At mach 25 it has a kinetic energy of 3,579,000,000,000J. So it turns out that the freight train only has 0.13% of the kinetic energy of the Shuttle. Shuttle wins, hands down.

And it makes sense when you think about it. Just think how much fuel the Shuttle has to take on as opposed to the relatively small tanks in the diesel engines. (Not to mention that the energy is proportional to the square of velocity, and not the square of the object's mass.)

College is funny.

P.S. Will it ever stop raining??

1 comment:

R2K said...


This web page talks about hypervelocity and even relativistic weapons and the energy they have in them.