# 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) Student riding rocket-powered cart video

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:

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.Thoughts on using technology:

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

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

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