The Drag Model

In this exercise you will further test the drag model by comparing it with the motions of cups of different masses. A good model should match the motions of lighter and heavier cups (using identical force functions and parameters) as well as it matches the mass 5 cup. (Note that there may be slight variations in initial velocity due to release times.)

Double-click the green arrow to open the video in Tracker. Note that the video has already been calibrated.

Click on the Tracker tab with your drag model from the previous Dynamic Modeling exercise (you may need to reopen the data file that you saved). Select the drag model and copy it to the clipboard. Then c lick again on the newly opened "CupClipsDrag" tab, paste a copy of the model, and change its name to "mass 5." Then paste twice more, assigning names "mass 8" and "mass 1".

Set the correct masses of the mass 1 and 8 models on the toolbar. Then, for each, open the model inspector by choosing "Model" in its track menu. Adjust the initial values for correct placement and best fit. Note: do not change the parameters or force functions!

Can you get the drag force model to match the motions of all three cups reasonably well? Can you now tell which of the two force types is a better model for air resistance?