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Next: Question 2 Up: Lakes as Well-Mixed... Previous: Question 1
Aiee!

Sorry...

A step input would mean that the gasoline would be entering the lake more or less steadily over a long period of time, which is not the case here. Instead, what we have here is better modeled by an impulse function.

The gasoline will in effect enter the lake suddenly and as a blob. For all intents and purposes, no gasoline will enter after that time, the initial time we might call t 0. So the impulse input function, while a little simplistic, is a good approximation to our input in this case. The graph of an impulse input function is shown below so you can see how this fits our case.

Impulse Graph

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John Hoggard <hoggard@math.vt.edu>
Last modified: Sun Aug 10 17:39:31 EDT 1997