At a Glance

• Physics

Instructional Level

• College & CEGEP
• University

• Mechanics

Social Plane(s)

• Group

• Collecting & seeking information
• Solving problems
• Analyzing
• Reviewing & assessing peers

Technical Details

Useful Technologies

• Computers or interactive whiteboards
• Tracker software

Class size

• Small (20-49)

Time

Single class period (< 90 mins)

Instructional Purpose

• Exploration & inquiry

• Array
• Array

Overview

In this activity, students will use the Tracker software to analyze projectile motion, then determine which equations fit the plots produced. (Video analysis and modeling tool - Tracker software)

In groups of 3-4, students go outdoors and take a video of themselves throwing an object, being careful to frame the video correctly and to include some means of distance calibration (such as a meter stick), and ensuring the camera does not move while they film. This can be done using a cell phone.

In this activity, students will use the Tracker software to analyze projectile motion, then determine which equations fit the plots produced. (Video analysis and modeling tool - Tracker software)

In groups of 3-4, students go outdoors and take a video of themselves throwing an object, being careful to frame the video correctly and to include some means of distance calibration (such as a meter stick), and ensuring the camera does not move while they film. This can be done using a cell phone.

Students then return to a computer or interactive whiteboard and upload this video into the Tracker software (for example by emailing themselves the video), and calibrate the axes and distances. They then track the object frame by frame as a point mass using the software, which uses this data to produce plots of position, velocity, and acceleration along both axes.

Students switch work stations with another group, analyzing the other group's work. They use the other group's plots to determine which equations best fit the data for each of the six plots, solving for any necessary coefficients.

At the end, the instructor can lead a class discussion of the equations and how they relate to one another, as well as what each coefficient means. This can also lead into a calculus-based discussion if appropriate.

Instructional Objectives

• Students learn to create and interpret kinematic plots describing an object’s motion, and learn the relationship between them.
• Students learn how to find an equation describing a plot, and gain a deeper understanding of why kinematic equations successfully describe motion.

Contributor's Notes

Sameer Bhatnagar

Dawson College, Montreal, QC

Benefits

Students create the graphs knowing that another group will be basing their work on them; this forces students to make well formatted and readable graphs and encourages them to keep their pace up.

Students begin to appreciate that kinematic equations don’t come from nowhere, for example that they would not correctly describe motion if the coefficients were different or if a cubic function were used rather than a quadratic. Students come to understand that each term has a role in making the big picture true.

Challenges

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.

The slow motion function on the motion tracker is tempting to use, but the algorithm behind it currently has bugs relating to the logged time difference – it should therefore be avoided.

Tips

Visual classrooms makes a great platform to upload and share documents into for this activity.

The acceleration-time graphs are very noisy (as with any method of tracking motion). For more advanced classes, this can lead into a discussion of why the data is noisy (propagation of uncertainties).

If students use a very large object, they may be confused as to what part of it to track. This can be a “teachable moment”, as they should use the center of mass.

This can be a useful activity to emphasize the concept of a model, especially in the wrap-up. The equations are your model, and the collected data are the “facts”. We therefore can create our model from the facts, and we could later test it in other scenarios.

This activity can be used along with the Motion Diagrams activity, with this activity being done after completing the acceleration vectors for an object in projectile motion and before students reevaluate their work. It is also useful to pair with the Energy Tracker activity, which can be used later in the year with the same software.