December, 2002, Middle School Experiment:

Fun with Friction Finale

- Purpose
- Background Information
- Equipment & Supplies
- Software & Probeware Setup
- Data Collection and Recording
- Data Analysis
- Conclusions and Extensions

PASPORT Force Sensor
(PS-2104)

PASPORT Force Sensor

ScienceWorkshop
Force Sensor
(CI-6746)

ScienceWorkshop Force Sensor

Purpose:

Explore the concept of static friction.

Background Information:

In this final installment on friction from Edward Nodding, we investigate Static Friction. It is often harder to get an object to start to move than to keep it moving. To see some interesting facts about friction, including a simulation, click on "Forces" at the website of Science Joy Wagon (must sign up at website to view this page).

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Equipment and Supplies:

For each lab group:


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Software and Probeware Setup:

  1. Tie a short string from the hook of the Force Sensor to the eyelet of the friction block.

  2. Setup your work space so that you have a clear area on your table or lab bench to drag the friction block with the sensor for several centimeters.

  3. Ensure that your USB Link, Xplorer or ScienceWorkshop 500 interface is connected to the computer and connect the Force Sensor to your computer interface.

  4. ScienceWorkshop 500 users: Click on one of the links below to download a pre-configured DataStudio workbook file for this experiment, and then open the file.

       SW Windows (.zip file) or SW Macintosh (.sit file)

  5. PASPORT users: Click on one of the links below to download a pre-configured DataStudio workbook file for this experiment, and then open the file.

       PS Windows (.zip file) or PS Macintosh (.sit file)

  6. Also, you can download a DataStudio file containing sample data:

       PS Windows (.zip file) or PS Macintosh (.sit file)

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Data Collection & Recording

Students will follow the on-screen instructions. Hint: to move through the pages in the Electronic Workbook, use the navigation buttons at the bottom of the page:


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Data Analysis:

Students will compare data from two trials: the first with the smooth side of the friction block and the second with the fuzzy side. There are two key concepts for students to recognize. The first is that different types of surfaces have different maximum static friction values even though the normal force is the same in each case. The second is that the general behavior for two different materials is roughly the same. Force is applied until it overcomes the static friction and the block begins to move. The force resisting motion is then just the sliding friction force.

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Conclusions and Extensions:

  • Place the friction block on a ramp that starts parallel to the ground. Slowly raise the end of the ramp closest to the block. At some point the block will begin to slide down the ramp. If the ramp is steep enough the block will slide all the way to the bottom.  Static friction will be strong enough to keep the block from starting to slide but sliding friction will not be strong enough to stop the block once it starts to move.

  • Can you think of a situation where there is a large static followed by a small sliding friction? Consider a car turning on ice. The sideways motion of the car is zero until the static friction between ice and tire is overcome. Once the static friction is overcome, the vehicle spins wildly (has a high degree of sideways motion)