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# Direct Measurement Video Analysis - Blow-Dart Collides With Cart

#### Summary

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This activity will allow students to analyze a direct measurement video clip of a blow dart colliding with a cart initially at rest. Students will be able to make measurements directly from the video that will allow them to investigate physics concepts such as velocity and conservation of momentum.

## Learning Goals

• Students will be able to use a video to measure the velocity of the dart and cart, before and after the collision.
• Students will be able to compare momentum before and after a collision.
• Students will become more familiar with using videos to directly measure physics concepts.
• Students will apply conservation of momentum to a real-world situation.

## Context for Use

This lesson is set up to introduce direct measurement videos. This activity should take about one 50 minute class time from introduction of material to the end of analyzing. The students should be familiar with basic physics concepts such as how to measure velocity, acceleration, and momentum mathematically. Generally, this would be useful for any introductory physics course. Using the video clip should encourage critical thinking. This lesson is based on showing how to use the video direct measurement for the first time. The teacher can give as much detail in the instructions as he/she wants, or be vague and give only the necessary numbers for calculations and let the students find the measurements on their own by trial and error. This activity has the capability of being used for direct instruction or inquiry based learning.

## Description and Teaching Materials

• Each student will need a computer to play the video on in order to analyze it. If there are not enough lap tops available, then the students may work in groups.
• This activity uses the Direct Measurement Video, Blow dart collides with cart. Students can access this video via the student video library which allows access to all videos for students, without links to instructor materials.
• Students will need to perform calculations so scratch paper, pencil, and calculator are useful.
• The following sheet can be handed out to the students to help keep them organized and provide questions for them to answer: Student Handout (Microsoft Word 28kB Jul13 12)
• In order to change the difficulty level of this lesson simply take out the questions that lead up to how to calculate the conservation of momentum and ask only questions 5-8.
• Here is an answer key for the student handout: Handout Answer Key (Microsoft Word 29kB Jul13 12)

## Teaching Notes and Tips

If a teacher plans to teach this lesson as an inquiry based lesson, it may be beneficial to have students in groups in order to facilitate questions and discussions.

This is set up to introduce direct measurement videos, so the first time the students see them they should be given time to play around with how the measurements could be found and how to use the frame counter or go frame by frame. The lesson may end up taking more than one class period depending on the knowledge of video software and background knowledge and comfort of physics equations needed.

## References and Resources

Student Handout (Microsoft Word 28kB Jul13 12)

Handout Answer Key (Microsoft Word 29kB Jul13 12)

physicsclassroom.com

Understanding conservation of momentum