Water Rocket Computer Model Problems

Answer to problem 6

Answer - 320 x 240 pixels GIF

I asked for an explanation for the following . . .
1. to find an explanation for the maxima that occur.

The moral of this story is double check your input parameters or Hey's Law "Garbage in - Garbage Out". In the question, I stated that the time I guessed the air impulse to be was 4 seconds. Not unreasonable. However, I input 4 into the Duration of air impulse box, forgetting that it was in milliseconds. The above output is the result of that mistake.

The reason for the maxima is that the air impulse is calculated in steps of 1ms and therfore the computer model takes the integer of the air impulse time ie 3.2 becomes 3.0 and 3.7 becomes 3.0. In fact, the variables page will not allow you manually to use anything other than whole numbers.

The band to the right of the 1ms line produces an error that is caused by the impulse being less than 1ms. To the left, there are the steps for 2, 3 and 4ms, blending off into a continuum.

If I had used 4000 instead of 4, the picture would have been completely different.

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