25 Sep 2016 - Modeling Air Resistance - Lab 4

Purpose: The purpose of this lab is to come up with a model for air resistance, which acting on a falling object, opposes the force of gravity.

Theory: Air resistance is a type of frictional force. It opposes motion in any direction. In this lab however, we will only focus on the effect it has on falling objects. Using coffee filters due to their ability to reach terminal velocity in freefall fairly easily, we can figure out the force that they are applying against gravity by using their velocities and masses.

Apparatus: Our apparatus was fairly simple; there was a long black drape that was used as a backdrop for a meter stick that was taped, and hanged off of a second-story balcony. Then coffee filters were dropped from the same balcony, and videos were recorded on our class laptops using logger pro. The meter stick was used to create a scale on logger pro, and the filters' motion was tracked and plotted on a graph by the software. The coffee filters were dropped 5 different times; they were stacked on top of each other in increments of 1,2,3,4, and5 coffee filters. After the motions were plotted by logger pro, we recorded the terminal velocities, given by the slope of the linear fit line. We then calculated the masses of the coffee filters using the fact that 150 filters had a mass of 134.2g.

The first three graphs below show the velocities of the filters in freefall. There was an error when the videos were recorded and we did not have data for 4 filters. The other graph is missing because I must have accidentally erased it. After we got all of the terminal velocities, we then plotted the velocities on a new sheet on the x-axis, with their respective masses on the y-axis and then we did a power fit line to generate a function, which was our model for air resistance. Air resistance was =k*v^n

k=constant=0.0003911+/-0.0001674

v=velocity=variable

n=power=3.299+/-0.6374

Conclusion: I do not think that this model works very well for air resistance as a whole. This is because this model is only for anything that is shaped like a coffee filter. Since air resistance is very dependent on the shape of the object moving through the fluid,  something as simple as inverting the filter will cause this model to be inaccurate.

 

Lab Partners were Cesar and Elliot