Attach a spring balance to the end of an empty box. Determine the force needed to start the box in motion, and then to keep it moving at a constant velocity. Place objects inside the box to increase its weight. Repeat the experiment. Develop generalizations regarding the coefficients of static and kinetic friction.
Athletic events involving motion at high speed pay particular attention to reducing air resistance.
Examples include such sports as downhill skiing, cycling. Students might enjoy researching some of the ways in which frictional forces are minimized in such sports. One way to do this activity is to divide the class into groups. Each group could research a different topic and make presentations to the class. Investigate ways in which the ends of a travois could be cut to reduce friction.