# Direct Measurement Video Analysis: Friction of a Block Sliding Down a Ramp

#### Summary

## Learning Goals

The objective of this lesson is for students to use a direct measurement video of a wooden block sliding down a ramp to calculate the coefficient of friction between the ramp and the block. To do this, students will have to apply what they have learned in class about forces and motion, vectors, and friction. Specifically, students will:

- apply their understanding of forces on a ramp to a real-life situation.
- demonstrate that they can separate the force of gravity into components perpendicular to and parallel with the ramp surface
- apply the relationship F
_{f}= u_{k}F_{N}. - demonstrate their ability to apply Newton's Second Law, F = ma in both the y- and x-direction.

## Context for Use

I would use this activity after students have learned about forces in two directions in an introductory, algebra-based physics course. This activity could be used after the lesson is taught to practice and reinforce the ideas that were just taught. If used right after the lesson, scaffolding may be required if the students have not yet mastered the concept. This activity could also be used a few days after learning about forces in two directions with little to no guidance to allow the students to show their mastery on the topic.

If a classroom set of laptops is available, each student can download this video and work on the activity individually for 10-15 min. Alternatively, they class could view the video together, projected on an screen in front of the class. Through classroom discourse, consensus can be reached on what measurements will be needed to complete the analysis. Next, I would either let them continue on their own or I would let them pair up to work with a partner for the remainder of the time. Depending on the student's exposure and practice to forces in two directions, this lesson make take 30 minutes up to 60 minutes. I would consider this activity more lab based because the students are working on their own or in groups and using discovery learning.

Note: This activity is being used with the assumption that this is not the first time the students have ever worked with a direct measurement video.

## Description and Teaching Materials

I would do this activity with my students after learning about forces in two directions. If my students have a very good grasp on the topic I would use the worksheet that is title "Little Guidance". This worksheet does not guide the students step-by-step, and really demands a lot of critical thinking done by the students. If my students did not have a very good understanding, I would use the worksheet that has the title "Scaffolding". This worksheet has a step-by-step process that walks them through the whole entire worksheet of finding the coefficient of kinetic friction. This worksheet does not demand a lot of independent critical thinking.

Description of the mechanics of this activity: See worksheet(s)

Video of Block Sliding Down a Ramp (Quicktime Video 5.2MB Jul13 12)

Block Sliding Down a Ramp Scaffolding with Answers (Microsoft Word 2007 (.docx) 237kB Jul13 12)

Block Sliding Down a Ramp Scaffolding with NO Answers (Microsoft Word 2007 (.docx) 75kB Jul13 12)

Block Sliding Down a Ramp with Little Guidance with Answers (Microsoft Word 2007 (.docx) 210kB Jul13 12)

Block Sliding Down a Ramp with Little Guidance with NO Answers (Microsoft Word 2007 (.docx) 72kB Jul13 12)

## Teaching Notes and Tips

- Make sure to have the video downloaded to a computer and ready to play in QuickTime at the beginning of class.
- Make sure to have the correct and enough worksheets printed.
- Make sure to allot enough time for the students to explore the physics activity.
- Students should have been exposed to direct measurement videos at least 5 time prior to this activity.

## Assessment

## References and Resources

Only reference used was the video of the block sliding down the ramp. This must be downloaded to a computer and played in QuickTime. Here is the link to the library of where it was selected:

https://serc.carleton.edu/sp/library/direct_measurement_video/video_library.html

Here is the downloaded video in QuickTime:

Video of Block Sliding Down a Ramp (Quicktime Video 5.2MB Jul13 12)