Friction of a Rolling Soccer Ball



normal force


        When a soccer ball moves along a surface, there is a component of force that is parallel to the surface. This parallel force is called the frictional force (Cutnell & Johnson). Frictional forces are always tangent to the surfaces. A soccer ball rolling across a field creates friction, the friction being opposite the direction the ball is traveling.

          Physics uses the equation  for objects that slide against one another. In the equation the frictional force (f) is equal to the normal force () multiplied by the coefficient of friction (). The coefficient of friction will vary with the ball and the type of surface with which it interacts. The more friction there is between the ball and the field, the slower the ball will move across the field.

          Therefore, the coefficient of friction will tell us how fast or slow a ball will travel. It only makes sense that the higher the coefficient of friction is, the slower the ball will travel (




An example found at


rolling diagram


          What happens if you kick a soccer ball without giving it any spin? – Your foot will give the ball an initial speed () and an initial angular speed of 0. The interaction of the ball and the grass will cause friction. The ball will initially slide across the field, start to rotate, and eventually start rolling without slipping. This will happen as its center-of-mass speed equals its angular speed (around its center of mass).

          Suppose you want to kick the ball so that it immediately starts rolling without slipping. How could you do this? You would give the ball “topspin” by striking the ball a distance (s) above an imaginary horizontal line that passes through the ball’s center. Where should you kick the ball in order to do this? The answer works out to be s=0.4R. You would have to kick the ball a little less than half the radius of the ball above its center line (as shown in the picture above).






Information for this page was obtained from:

Cutnell & Johnson Physics. Volume 1. 6th Edition.