Lab 6 - Drag force on a Coffee Filter

Objective:  To study the relationship between air drag forces and the velocity of a falling object.

Procedure: Using coffee filters as the falling object, we were to track the velocity using the logger pro software and the motion detector.  To do this, we started with 9 of the coffee filters about a meter and a half above the motion detector and let them fall freely until they hit the floor.  The motion detector and the logger pro software would track the position over time.  Using the curve fit for a sample in the graph that was created, we were able to determine the velocity of the falling filters.  Then with excel, we tracked this motion for 5 trials and determined an average velocity of the 9 filters.  One of the filters was removed from the stack and the procedure started all over.  After the five trials were captured, another filter was removed and the same procedure followed. This continued until there was only 1 filter, and five trails were completed.  A copy of the excel sheet is posted below.

The information that was used to populate this table was pulled from the position versus time graphs that were created with the logger pro software, and the curve fit that was used to get the

Questions:
1) In the formula F-drag = K V^n, what should the n be?  The n should be a 2.  The velocity would be parabolic in nature since it is being increased by the weight (f-gravity * mass) exponentially.  This  would be true until the object reaches terminal velocity where f-drag = weight.
2) Why is it important that the shapes stay the same? Since we are experimenting with the drag force, and this is directly effected by the cross section of the object, any change in the shape of the object is going to change the cross section and therefore have an effect on the drag of that object.
3) What should the position versus time graph look like? Explain. Since the object is falling over time, the graph should be a straight line representing the distance from the sensor as time goes by.  Therefore, the shape of the graph would be a slope.
4) What should this slope represent? Explain.  Once the object can no longer accelerate, where f-drag = weight, then the object has reached terminal velocity.  Terminal Velocity is where a falling object can no longer accelerate because the drag force and the gravitational force plus mass are in an equilibrium.
5)

PSOE:
1) As stated in question 2, the shape of the coffee filters should be relatively the same no matter the count used for the experiment.  Our set of filters were slightly worn, and no matter how much we tried to keep the shape consistent, they always seemed to lay out as flat again.  This lessened somewhat as the experiment went on, but it did seem to have an adverse effect and this was really seen in the average velocity over time chart that was published in the procedure.
2) As always, the tools and equipment that were used are not the most precise ones available.  This does not prevent us from doing the experiments, just makes our results a little fuzzy.
3) Try as much as I did, but I am sure that I was not able to drop the filters from the same position every single time.  For the trials where the numbers seemed extremely different from the other trials, the trial was repeated to try to minimize this as a source.
4) No matter how many times I explained to one of the lab partners that the motion detector picks up movement in a cone, he still insisted on waving the measuring stick in front of, and around the testing area.  This also lead to several of the trials being run again in an effort to remove this as a source.

Conclusion:
The experiment was a very time consuming one.  Between the number of trials that had to be ran again due to the sources of error that were explained, and the fact that there were 45 base trial runs, this turned into a lengthy experiment.  That is not to say it was a boring or tedious experiment, just a long one.  This ended up being one of the reason that some of the trials that needed to be redone were not.  We simply ran out of time and barely got the lab completed as class was ending.
One thing that should have been done was to control the area around the experiment a lot better.  I think that this might have helped tremendously with the numbers that were calculated from our trial runs.