A box with a weight of 50 N is at rest on a flat surface. A force F directed to the right is then applied, starting from 0 and building up until the box starts to move. The coefficient of static friction between the box and the surface is 0.6, while the coefficient of kinetic friction between the box and the surface is 0.4. Graphs of the magnitudes of the force and the opposing friction force are shown on the right.
Modified from Andrew Duffy's web page at Boston University. The animation uses the Physlet Java Applets of Wolfgang Christian and Mario Belloni.