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Mathematics Goes to the Movies

by Burkard Polster and Marty Ross


Thirteen Conversations About One Thing (2001)

PROFESSOR: A car is traveling at 30 miles per hour when he sees the pedestrian 150 feet ahead. Using this equation we find that reducing the velocity to zero requires a constant deceleration of 6.45 feet per second squared.
STUDENT: Don’t you have to assume that the car’s velocity remains constant during the deceleration period?
PROFESSOR: Yes, you are right. The constant in this case is an average. A better example of nearly constant deceleration is constant freefall of a body near the Earth’s surface, a pair of glasses dropped from a building, for example. Any more questions before we move on?

PROFESSOR: We can determine the range R with this equation. An object projected horizontally will reach the ground at the same moment as a free-falling one dropped from the same height.
STUDENT (Mr Hammond): Even if one of them is significantly…
PROFESSOR: There are no “ifs”. Physics is an exact science. The laws of the universe are absolute.

PROFESSOR: I see Mr. Hammond is late again, hmm.
STUDENT: There was a party last night. He fell from the top of the math building onto the quad.
OTHER STUDENT: No, he didn’t. The range is too great. If he had fallen, he would have landed near the bushes. He must have jumped, wouldn’t that be right, Professor?