March 11, 2015: Air Risistance

Purpose:
The Purpose of this lab was to find out how air resistance behaved with falling objects and how this led to the objects having a terminal velocity. In other words, the relationship between air resistance  and the speed of falling objects (in our lab, coffee filters).

Set-up:
The stage for this experiment was the technology building, also know as building 13. The reason for the selection of this building and not just any other place is because the building has this balcony indoors where there are no air currents. This allows us to have a better chance to only deal with vertical air resistance.

Photo taken from balcony where coffee filters were dropped to to the ground
The laptops that were going to record the fall are seen on the stairs.

For this experiment we measured the glass part of the balcony at 1.5m and put this into the scale for our video recording. We dropped air filters from the top and recorded their path to the bottom. On the first run we used only one filter, the next run we added another filter and saw it glide down and proceeded to add one and repeat for 5 times. We then returned to class and began to analyze the videos on logger pro.

We analyzed each video and plotted points to obtain a graph of each acceleration like this one:

Once we had the terminal velocity of each round of coffee filters, we proceeded to obtain the mass of the air filters. Our classmates did the calculations and obtained the value of one coffee filter to be 0.000926Kg. With the information now being sufficient we went off to find a mathematical model to simulate what we had seen. It turns out the equation F= K * (V^n) is our equation for air resistance and K is simply a sensitive value for surface area in contact with the air on the bottom. Once we graphed the combined known values of mass and terminal velocities and created a exponential graph fit we obtained the following graph:

The computer then gave us a value, but just to be sure we used Excel to analyze our data and also calculate our value of air resistance. Using Newtons second law of F=ma we came to the conclution that a=g[(K*V^n)/m]

As we see here, when our acceleration is about 0, our velocity is 1.8867m/(s^2). With a percentage error ~+or - 1%.

Conclusion:

We were able to get a good idea of what air resistance is. In essence it is when the force of the air is the same as the mass of the object falling, thus rendering the acceleration equal to zero. Although we could not completely prove this thru our lab because of uncertainty in the lab equipment, we know this to be true as we came really close.