Falling Object Tracker

In this activity, students will be using the Tracker software to analyze the acceleration of two falling object.

In groups of 3-4, students go outdoors to record two videos of falling objects. This is done as a class, however each group will take their own videos. Students should ensure that a distance calibration tool is visible in the video, that the camera is stationary throughout the duration, and that they are far enough back from the objects that the angular geometry does not interfere significantly with their results. The first object, a soft rubber ball, is dropped from a high place by students or the instructor (for example the roof or a high window of the school). Students should ensure that at least one member of their group is filming using their phone. This is repeated for the second object, a light object hanging from the handle of an open umbrella.

Students then return to a computer and upload the first video into the Tracker software (for example by emailing themselves the video), and calibrate the axes and distances. They then track the object using auto-tracking function of the software (or manually if needed), which produces tabulated data for the position as a function of time.

Students import the data into a spreadsheet program such as Excel. Students use the data to produce data for the velocity as a function of time, then plot the position and velocity, using the latter to find the acceleration (taking the slope). This is repeated for the second video.

Groups can then discuss the differences between the two problems, paying attention to the role that drag forces play in determining the terminal velocity of each object. They may also compare the acceleration found for the first object to the acceleration due to gravity.

Students learn to analyze 1d kinematic problems and see examples of both constant velocity and constant acceleration. Students learn to analyze and plot data using spreadsheet software.