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[Phys-L] Re: Aristotelian thinking among modern students



At 01:19 PM 10/20/2005, you wrote:
I ask this SAME question on my test. Students think inertia is a force.
They also believe that if v = 0, then a = 0 This is very difficult to
teach, and to understand.


It wasn't so many years ago that a contributor offered a question
on this list: if I drive a car up a slope then engage neutral,
the car slows and reverses, trickling back down the slope.
The velocity is graphed by a straight line slope, dipping through
zero at the car's high point.
The acceleration on such a graph would be a straight
horizontal line. That is, it is non-zero, when the velocity
goes through zero.

Now consider the case when I drive forward, coast to a standstill,
and at the moment the speed is zero, I apply the brake.
What is the physical significance of the acceleration dipping
suddenly to zero?

As I recall, this created some debate....


Brian Whatcott Altus OK Eureka!