# Using a Direct Measurement Video to Find the Rotational of Inertia of a Bicycle Wheel

#### Summary

## Learning Goals

- Students will apply the concepts of angular acceleration, torque, and rotational inertia, as well as Newton's Second Law for rotation, to a real-world situation.
- Students will apply the relationship between linear and angular motion for a rotating object.
- Students will practice collecting data from direct measurement video.
- Students will also rely on their prior knowledge of one-dimensional force analysis of an object that is accelerating.
- Students will also develop collaborative learning behaviors while working together.

## Context for Use

This activity is intended for an algebra-based physics course in a technical college. Class size ranges from 20-24 student in a lab setting with available computers or laptops. Depending on the amount of introduction included for the activity, the students should take between 30 minutes to an hour to complete. No additional equipment is required to complete the activity, but could be supplemented with a physics style bicycle wheel apparatus or a pulley system. This activity is not intended to be students' first exposure to using direct measurement video.

Prior to the activity, students should have a strong grasp of accelerating systems, experience with connect object problems, circular measures, and Newton's Laws of Motion. The activity is planned to be used in a 2 hour lab/lecture setting. The material regarding angular motion and moment of inertia will be introduced, the activity will follow, and the class will finish up with a discussion of our findings. Depending on the skill levels of the students, the activity should be easily adapted to other settings by including more detail/information of the introduction.

## Description and Teaching Materials

The description of the material, verbal instructions for students, and possible follow up question can be found in the following word document:

Moment of Inertia for Bicycle Wheel (Microsoft Word 29kB Jul13 12)

The video relating to the material can be found at the following website:

Bicycle Wheel Accelerated by Falling Weight

The video must be downloaded to students' computers and opened in QuickTime to be able to advance the video frame-by-frame.

## Teaching Notes and Tips

This activity is sectioned into 3 parts: presentation of material, student analysis of the video, and discussion. The presentation of material should contain similar problems relating to the video. The analysis of the video will probably take up the majority of the activity. Discussion is used to confirm that students are grasping the material. Out of a 2 hour class period, I would present the material for 1/2 hour, let the students analyze the video for an hour, and then use the last 1/2 hour for discussion, questions, and comments.

If students do not have experience using direct measurement videos, the
instructor should expect to spend some time helping students understand
how to make measurements from the video. For example, students may need
some tips to see that they can use the frame counter and the frame rate
to find the elapsed time for the suspended mass to fall.