# Using Direct Measurement Video to find the acceleration of a rocket-powered cart

#### Summary

A video of a student accelerating across a stage on a cart powered by a
releasing compressed carbon dioxide from a fire extinguisher can be used
to analyze constant acceleration. This video includes a to-scale ruler
that students can use to find displacement, as well as a frame counter
that can be used to find elapsed time. This lesson is meant to be a
direct application of using the kinematic equations to solve for the
acceleration of the cart.

## Learning Goals

- Students will be able to identify physical quantities (variables) that are necessary to use in the equations of motion for constant acceleration.
- Students will be able to rearrange kinematic equations to solve for an unknown quantity.
- Students will be able to solve for the acceleration of an object using kinematic equations.

## Context for Use

This
lesson is designed for students in either Conceptual Physics or College
Prep Physics as a direct application of the kinematic equations to find
acceleration given initial velocity, elapsed time, and displacement.
As an open-ended question (see "Teaching Tips and Thoughts") this
lesson would be appropriate for use in an AP or IB Physics course.

## Description and Teaching Materials

1) Video of student riding a rocket-powered cart

Note: Right click on the link and download the video to your hard drive as a QuickTime video. If you simply click the link, you will not be able to view the video using a frame-by-frame analysis.

2) Student Instructions (Microsoft Word 25kB Jul13 12)

3) Teacher Solutions (Microsoft Word 33kB Jul13 12) (with solutions and hints)

Note: Right click on the link and download the video to your hard drive as a QuickTime video. If you simply click the link, you will not be able to view the video using a frame-by-frame analysis.

2) Student Instructions (Microsoft Word 25kB Jul13 12)

3) Teacher Solutions (Microsoft Word 33kB Jul13 12) (with solutions and hints)

## Teaching Notes and Tips

This
lesson is written in a way that students with minimal experience using
direct measurement video analysis could succeed with minimal teacher
intervention.

Thoughts on differentiating this lesson:

To make this lesson less scaffolded, you could simply ask the students to use the video to find the acceleration of the cart. You might simply tell them that the video shows a cart accelerating uniformly. This would be appropriate as an assessment after students have mastered solving uniform acceleration problems and had some experience using direct measurement videos. It would also make the problem more appropriate for an AP Physics student.

You could also include uncertainty estimates for the measurements taken in the video.

Thoughts on using technology:

This lesson could easily be adapted for use with online homework software, such as Quia or WebAssign.

Thoughts on differentiating this lesson:

To make this lesson less scaffolded, you could simply ask the students to use the video to find the acceleration of the cart. You might simply tell them that the video shows a cart accelerating uniformly. This would be appropriate as an assessment after students have mastered solving uniform acceleration problems and had some experience using direct measurement videos. It would also make the problem more appropriate for an AP Physics student.

You could also include uncertainty estimates for the measurements taken in the video.

Thoughts on using technology:

This lesson could easily be adapted for use with online homework software, such as Quia or WebAssign.

## Assessment

This
assignment is meant to be a simple problem that requires students to
use kinematic equations to solve for the acceleration of an object. A
simple assessment would be to give the students another video that
requires them to find the acceleration of a different object, but this
time to not lead them through the process step-by-step. Another idea
would be to create a "puzzle" video, where you give students either
elapsed time between two points and the acceleration and require them to
solve for distance traveled. Any combination of variables could be
given and the student could be required to solve for the unknown.

## References and Resources

Direct Measurement Video Library

Video credit to Peter Bohacek, Henry Sibley High School (peter.bohacek@isd197.org)

Video credit to Peter Bohacek, Henry Sibley High School (peter.bohacek@isd197.org)