Friday, September 2, 2016

Alex's First Honors Physics Assignment


Song:  Right Down The Line

Artist:  Gerry Rafferty



Alex first assignment in his Honors Physics class had him use an online 
ballistics calculator which, with the input of variables, could determine
the outcome, in raw data, of an object with such forces applied to it.

The assignment directed the students to change one of the variables...
and to keep all the others constant, and to then complete a paper 
using the raw data to support a conclusion.








I know...
in the real world...
only very slow projectiles or objects could have a negative drag coefficient...
and it could only be considered as such if a contributory force traveled along
the original line of force and which were faster than the object...
 and if it were to be considered as a negative drag coefficient in the formula.

Example:

A thrown basketball.

The thrust would have been the force used to initially propel it...
and would have given the ball its initial speed...
which would have degraded steadily along its path because of drag..and gravity.

Now, say...a wind were blowing in the direction of the trajectory of the ball...
and it were blowing faster than the ball were traveling...
and it not only cancelled the drag...it had pushed the ball farther.
The drag could then be thought of as less than none...
 a plus force...or...a negative drag.

A sail is actually a horizontally applied force, air foil.
It has a negative drag coefficient as the lower pressure is on the forward facing
direction of travel and the higher pressure is in the rearward facing portion.

It has extreme drag to the applied force of the wind...by design.
However, since the wind is going faster than the boat...
and the designed drag is what gives its thrust...
along with it pulling by having lower pressure towards the direction of travel
as a result of the wind making it an airfoil...
there is not only no drag to its forward motion 
(strictly the sail...unless the current were also traveling faster than the boat...
and pushing it from behind)...
it is a negative drag...
it adds to its forwards motion
(just as an airplane's airfoil defeats gravity by creating higher pressure below...
and lower pressure above).

Although the experiment would have very few real life applications...
except in certain circumstances...
it was the usage of the data to complete an experiment 
that was the thrust of the paper.

I had talked to Alex about the highly implausible 
and extremely limited usage of the real life applications 
of a null or negative drag coefficient ballistics experiment...
and also about the circumstances where it could be applied...
such as in the above.


However...
Alex had conducted the experiment...
and had written up and completed this paper in about two hours.


So...
it was in the setup of an experiment using just the ballistics calculator
and the simple instructions of changing only one variable multiple times...
and to then write an experimental paper on the results
which was the actual lesson.











Alex is really enjoying all of his classes.

I used to greatly fear Alex learning how to drive.


I now dread Alex moving closer to the day he goes off to university.
However, as his parents, it is our job to ensure his wings are strong...
and that he is ready to soar when the time comes...
plus...we can always relocate our nest to be near his eventual nest  :)

My wife is already looking forwards to babysitting for Alex...
once he decides to start a family of his own...
in 15 - 20 years  :)















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