Based on what they have already learned about friction, students formulate hypotheses concerning the effects of weight and contact area on the amount of friction between two surfaces. In the Associated Activities (Does Weight Matter? and Does Area Matter?), students design and conduct simple experiments to test their hypotheses, using procedures similar to those used in the previous lesson (Discovering Friction). An analysis of their data will reveal the importance of weight to normal friction (the friction that occurs as a result of surface roughness) and the importance of surface area to the friction that occurs between smooth surfaces due to molecular attraction. Based on their data, students will also be able to calculate coefficients of friction for the materials tested, and compare these to published values for various materials.
Each TeachEngineering lesson or activity is correlated to one or more K-12 science, technology, engineering or math (STEM) educational standards.
All 100,000+ K-12 STEM standards covered in TeachEngineering are collected, maintained and packaged by the Achievement Standard Network (ASN), a project of JES & Co. (www.jesandco.org).
In the ASN, standards are hierarchically structured: first by source; e.g., by state; within source by type; e.g., science or mathematics; within type by subtype, then by grade, etc.
Click on the standard groupings to explore this hierarchy as it applies to this document.
- Common Core State Standards for Mathematics: Math
- 3. Fluently add, subtract, multiply, and divide multi-digit decimals using the standard algorithm for each operation. (Grade 6)  ...show
- a. Decide whether two quantities are in a proportional relationship, e.g., by testing for equivalent ratios in a table or graphing on a coordinate plane and observing whether the graph is a straight line through the origin. (Grade 7)  ...show
- 1. Construct and interpret scatter plots for bivariate measurement data to investigate patterns of association between two quantities. Describe patterns such as clustering, outliers, positive or negative association, linear association, and nonlinear association. (Grade 8)  ...show
- International Technology and Engineering Educators Association: Technology
- Next Generation Science Standards: Science
- Plan an investigation to provide evidence that the change in an object's motion depends on the sum of the forces on the object and the mass of the object. (Grades 6 - 8)  ...show
- North Carolina: Math
- Solve real-world and mathematical problems involving area, surface area, and volume. (Grade 6)  ...show
- Use ratio and rate reasoning to solve real-world and mathematical problems, e.g., by reasoning about tables of equivalent ratios, tape diagrams, double number line diagrams, or equations. (Grade 6)  ...show
- Fluently add, subtract, multiply, and divide multi-digit decimals using the standard algorithm for each operation. (Grade 6)  ...show
- Display numerical data in plots on a number line, including dot plots, histograms, and box plots. (Grade 6)  ...show
- Solve linear equations in one variable. (Grade 8)  ...show
- Summarize, represent, and interpret data on a single count or measurement variable (Grades 9 - 12)  ...show
- North Carolina: Science
- Predict the effect of a given force or a change in mass on the motion of an object. (Grade 5)  ...show
- 1.01 Identify and create questions and hypotheses that can be answered through scientific investigations. (Grade 7)  ...show
- 1.02 Develop appropriate experimental procedures for:
• Student generated questions. (Grade 7)  ...show
- 1.04 Analyze variables in scientific investigations:
• Identify dependent and independent. (Grade 7)  ...show
- 1.05 Analyze evidence to:
• Explain observations. (Grade 7)  ...show
- 1.06 Use mathematics to gather, organize, and present quantitative data resulting from scientific investigations:
• Measurement. (Grade 7)  ...show
- Understand motion, the effects of forces on motion and the graphical representations of motion. (Grade 7)  ...show
- Explain the effects of balanced and unbalanced forces acting on an object (including friction, gravity and magnets). (Grade 7)  ...show
- Understand the relationship between forces and motion. (Grades 9 - 12)  ...show
- Classify frictional forces into one of four types: static, sliding, rolling, and fluid. (Grades 9 - 12)  ...show
- Explain work in terms of the relationship among the applied force to an object, the resulting displacement of the object and the energy transferred to an object. (Grades 9 - 12)  ...show
- Students should be familiar with the information about friction covered in the Discovering Friction lesson, and the experimental method for measuring friction used in the Associated Activity Sliding and Stuttering.
- It will be helpful if students know how to prepare a line graph from data consisting of two variables.
- Students will be able to describe the effects of weight on normal friction, i.e., the friction due to surface roughness.
- Students will be able to describe the effects of contact area on the friction that occurs as a result of molecular attraction.
Lesson Background and Concepts for Teachers
|an empirically derived quantity for a pair of surfaces that is equal to the amount of friction measured divided by the weight of the object being moved|
|a resistance to motion that occurs when two surfaces are in contact with each other|
|the resistance to motion that occurs once one surface is in motion, sliding against another surface|
|the resistance to motion that must be overcome in order to allow one surface to begin sliding against another surface|
- Does Weight Matter? - Working in small groups, students design and conduct simple experiments to test for the effects of weight on friction.
- Does Contact Area Matter? - Working in small groups, students design and conduct simple experiments to test for the effects of contact area on friction.
- Students may be asked to write paragraphs explaining how and why weight affects normal friction, and how and why contact area affects friction due to molecular attraction.
- Students can be given data consisting of the weights and frictional forces measured for several pairs of surfaces, and asked to calculate the coefficient of friction of each.
Lesson Extension Activities
Other Related Information
Mary R. Hebrank, Project Writer and Consultant, Pratt School of Engineering, Duke University
© 2004 by Engineering K-Ph.D. Program, Pratt School of Engineering, Duke University
including copyrighted works from other educational institutions and/or U.S. government agencies; all rights reserved.
Engineering K-Ph.D. Program, Pratt School of Engineering, Duke University
Last modified: December 1, 2015