Return to Physics IndexFRICTIONJim Szeszol Mendel Catholic High School 250 East 111 Street Chicago, IL 60628 1-312-995-3700OBJECTIVES:To study the effects of friction in a simple mechanical system.APPARATUS:1) Self propelled dynamics cart (coil spring driven) 2) Meter stick 3) stopwatchProcedure:1) Perform "Hookes Law" experiment for coil spring constant 2) Determine distance and time for PE transfer 3) Calculate KE transfer for a) Translational KE b) Rotational KE - wheels, pulleys, axles 4) Determine the efficiency of the system Calculations : Determine the difference in energy levels using KE formulas for energy of translation and rotation. The ratio of kinetic energy of the cart to the potential energy of the spring will yield an efficiency value for the system. Conclusion : In most first year physics courses energy lost to friction is traditionally ignored. Through this activity the observation can be made that a significant (80% - 90%) of the system energy is lost to frictional forces while doing useful work.Extensions / Modifications :For translational KE only keep the ratio of rotational mass to translational mass small. example - small wheels - light wheels - single pulley - added mass to cart. For non-uniform motion - the cart will accelerate at rates dependent on the coil spring constant and the selected step pulley. To study these rates a timer tape can be attached to the cart to determine varying rates of motion.