Overview

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 ...

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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.

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Objectives

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.

Context and requirements

Level Grade 12-U0
Discipline Physics
Course Mechanics
Activity Content 1d Kinematics
Technological Requirements Computers or interactive whiteboards with Tracker software are required, as is excel.
Students will also need to take a video with their phone and access it with the computer (for example by email).
Best Use Practice, Lab

Author’s Notes

Benefits

Students learn to analyze and plot data and learn to work with spreadsheets, including using formulas and plotting.

Students take something out in the real world and analyze it in the physics classroom. Despite this, the activity hits many important learning objectives. By using their own phones to film this, the activity becomes more personally relevant for students.

Challenges

As students are using real world data, it can get messy. The deviation from ideals can confuse students; for example the umbrella sways back and forth and can even be blown sideways by the wind. You may have to help them through, suggesting they either choose smaller segments of the graph to analyze or take the average.

One challenge to this activity is that it has dependencies on several technologies, and it is therefore important to test everything beforehand. You should test your workstations, making sure you can take a video with your phone and get it onto the stations where students are working, then upload it into the motion tracker.

Tips

This activity can be paired with the other Tracker activities to promote continuity and familiarize students with the software. Specifically, this activity is designed to be completed prior to the Bottle Rocket Tracker activity.

You will want to ensure that you use brightly coloured objects (of a colour that does not show up in the background where you take your video) to ensure that the auto-tracking functions correctly. Green tends to be picked up well.

For the drop, students can organize themselves into teams which take on different roles. Students should think about going farther back, for reasons relating to the geometry, and you can get students to reason how this will affect their data.

Activity Pedagogical Components

Data Collection

As a CLASS, students record a video of an object in freefall and an object attached to an umbrella. Each group of students should have at least one member taking a video. This is done IN CLASS.

Data Analysis

Working in GROUPS, students use the Tracker software to analyze their data for the first object (freefall) and output it into excel. This is done IN CLASS.

Problem Solving

In GROUPS, students analyze the position and velocity vs time graphs, using the latter to determine the acceleration of the object. The analysis is then repeated for the second object, for which they can determine the acceleration both at the beginning of its motion and after it reaches terminal velocity. This is done IN CLASS.

Consolidation

In GROUPS, students discuss the differences in the motion of the two objects, paying close attention to the role that drag forces play. This is done IN CLASS.

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