With a simple demonstration activity, students are introduced to the concept of friction as a force that impedes motion when two surfaces are in contact. Then, in the associated activity, Sliding and Stuttering, they work in teams to use a spring scale to drag an object such as a ceramic coffee cup along a table top or the floor. They use the spring scale to measure the frictional force that exists between the moving cup and the surface on which it slides. By modifying the bottom surface of the cup, students experiment to find out what kinds of surfaces generate more or less friction. They also discover that both static and kinetic friction are involved when an object initially at rest is caused to slide across a surface.