Factors Affecting Friction

http://www.teachengineering.org/view_lesson.php?url=collection/duk_/lessons/duk_friction_smary_less2/duk_friction_smary_less2.xmllessontext/xmlFactors Affecting FrictionEngineering K-Ph.D. Program, frictionstatic frictionkinetic frictioncoefficient of frictionfrictionstatic frictionkinetic frictioncoefficient of friction

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.

Engineers must understand how friction affects a number of situations, from the bottom of skis in which friction is a disadvantage to hiking boots where friction provides traction. Scientists must think like engineers when designing experiments as the students do in both of the associated activities. 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. 3TeachEngineering.orgMary R. Hebrank (Project Writer and Consultant), Pratt School of Engineering, Duke UniversityS101DA63North_CarolinaMath2.01 Estimate and measure length, perimeter, area, angles, weight, and mass of two- and three-dimensional figures, using appropriate tools.66S101F83ENorth_CarolinaMath2.02 Solve problems involving perimeter/circumference and area of plane figures.66S10037F9North_CarolinaMath5.04 Use graphs, tables, and symbols to model and solve problems involving rates of change and ratios.66S1019570North_CarolinaMath2.02 Solve problems involving volume and surface area of cylinders, prisms, and composite shapes.77S1014376North_CarolinaMath4.01 Collect, organize, analyze, and display data (including box plots and histograms) to solve problems.77S101F39ENorth_CarolinaMath5.01 Identify, analyze, and create linear relations, sequences, and functions using symbols, graphs, tables, diagrams, and written descriptions.77S1028413North_CarolinaScience1.01 Identify and create questions and hypotheses that can be answered through scientific investigations.66S1028415North_CarolinaScience1.02 Develop appropriate experimental procedures for: • Student generated questions.66S1028419North_CarolinaScience1.04 Analyze variables in scientific investigations. • Identify dependent and independent.66S102841ENorth_CarolinaScience1.05 Analyze evidence to: • Explain observations.66S1028421North_CarolinaScience1.06 Use mathematics to gather, organize, and present quantitative data resulting from scientific investigations: • Measurement.66S1028428North_CarolinaScience1.08 Use oral and written language to: • Defend conclusions of scientific investigations.66S10284AFNorth_CarolinaScience1.01 Identify and create questions and hypotheses that can be answered through scientific investigations.77S10284B1North_CarolinaScience1.02 Develop appropriate experimental procedures for: • Student generated questions.77S10284B5North_CarolinaScience1.04 Analyze variables in scientific investigations: • Identify dependent and independent.77S10284BANorth_CarolinaScience1.05 Analyze evidence to: • Explain observations.77S10284BDNorth_CarolinaScience1.06 Use mathematics to gather, organize, and present quantitative data resulting from scientific investigations: • Measurement.77S10284C4North_CarolinaScience1.08 Use oral and written language to: • Defend conclusions of scientific investigations.77S1028520North_CarolinaScience6.03 Evaluate motion in terms of Newton's Laws: The force of friction retards motion. 77S1028527North_CarolinaScience6.05 Describe and measure quantities that characterize moving objects and their interactions within a system: • Time.77S1028531North_CarolinaScience1.01 Identify and create questions and hypotheses that can be answered through scientific investigations.88S1028533North_CarolinaScience1.02 Develop appropriate experimental procedures for: • Student generated questions.88S1028537North_CarolinaScience1.04 Analyze variables in scientific investigations: • Identify dependent and independent.88S102853CNorth_CarolinaScience1.05 Analyze evidence to: • Explain observations.88S102853FNorth_CarolinaScience1.06 Use mathematics to gather, organize, and present quantitative data resulting from scientific investigations: • Measurement.88S1028546North_CarolinaScience1.08 Use oral and written language to: • Communicate findings.88United StatesCopyright 2012 - Engineering K-Ph.D. Program, Pratt School of Engineering, Duke Universityhttp://www.teachengineering.org/policy_ipp.phphttp://www.teachengineering.org/2008-09-267Teacher