Why Is Static Friction Greater Than Kinetic Friction?

Static friction is greater than kinetic friction because of irregularities between the static object and the surface upon which it rests. The irregularities mesh together making it more difficult to start movement than to keep the object in motion.

Static friction is the friction that keeps an object in place. This friction must be overcome by energy to move the object. Because of a combination of surface irregularities and electrical charges between the object and the surface, the energy required to initially move the static object is greater than the energy required to keep it in motion. Because it takes more energy to move the static object, physicists say that static friction is greater than kinetic friction. The smoother the object and the smoother the surface the smaller the difference between the amount of static friction and the amount of kinetic friction.