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[Phys-L] Analyzing movies: Speed, with Keanu Reeves



Hello,

I do a number of exercises in class where we analyze scenes from movies,
or advertisements in magazines, for their treatment of physical reality.
After doing a calculation for the a particular scene in the movie
"Speed", with Keanu Reeves, I was somewhat surprised. I was wondering
if anyone else has done this, and are there other good movie scenes
which you have used?

The scene in question is a jump across a gap in a bridge of 50 ft, by a
bus going about 70 miles an hour. Now, it is unclear in the movie if
there is a ramp, and how much of one there is (the scenes conflict
somewhat from one time to the next). Barring that, could a bus manage a
50 ft jump at 70 mph, and what would it take to do it? If you treat the
bus as a particle, :), one calculates a take-off angle of a little less
than 5 degrees necessary to get across, which doesn't seem like a whole
lot to me. I could even accept that I wouldn't recognize a 5 degree
ramp at the end of the bridge from the distances shown in the movie.

Now, I imagine that the worst part of this is the "particle" assumption.
Certainly any rotation of the bus would cause it to land on its side.
There may be friction losses that I am not accounting for also. Is
there anything else major that is missing here?

I made sure to tell my students not to do this at home. :)

In addition to "Speed", I also like going through an analysis of
Armageddon, where the physics is *really* bad. I was surprised,
however, that the "Speed" bus-jump was not *completely* ridiculous from
initial calculations, just not particularly plausible.


Brian Blais

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bblais@bryant.edu
http://web.bryant.edu/~bblais