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Name: Jonas M.
Status: educator
Age: 20s
Location: N/A
Country: N/A
Date: 2/15/2004


Question:
I have a large debate with fellow teachers and students. A student went to the Grand Canyon in USA. He was told that a couple had argued in a car and the driver got so mad he drove off the cliff. Our argument is over how the car falls? Some theorize that the car will fall nose first and hit the bottom with the front bumper. They use the fact of the engine weight and aerodynamics to support their case. Others theorize that the car will tumble, or turn and twist a little and it will be too hard to tell which way it will fall. The engine weight is not critical in the fall compared to the rest of the car, and the car's mass is too big for aerodynamics to play a role.


Replies:
Although I have never driven a car off a cliff, in theory I would agree with your first group. I sense that the most import part of the problem is the aerodynamic force. Each given position on the car has momentum that is proportional to its mass. The greater the momentum, the more difficult it is to change its path. Therefore, the aerodynamic force (drag) will have a greater effect (i.e. a slowing effect) on the less massive portions of the car. I suspect the engine will lead the fall... because I expect that to be the most massive portion of the car. If you wish to test this hypothesis, I suggest driving a front-engine Chevy and a rear- engine VW off the cliff and see if indeed the engine does hit first in each case. You would, of course, need a high enough cliff to note the difference definitively.

This is much like the arrow problem. When the arrow moves through the air, the more massive head is less effected by the slipstream of the air than is the lighter end... which is also equipped with feathers to increase the drag.

I suggest a rock on the accelerator if you conduct the above experiment. Perhaps model cars run off a balcony might even be a safer - and reasonably accurate - test of my theory.

Larry Krengel



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