Friction

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As the ball is kicked across the surface of the field or through the air there is always a force acting in the opposite direction of motion. If the ball is on the ground this opposing force is called the frictional force, if the ball is in the air it is called drag. These forces are what causes the ball to slow down or as it moves.
Friction is caused when two surfaces are in contact with one another and drag which is also called air friction is caused whenever an object moves through the air or a fluid. In soccer friction is something the players have to overcome to make the ball move along the ground and through the air. It is also used to curve the ball along the ground using the spin of the ball and the frictional forces opposing that spinning. Friction also requires that the player kicks the ball with more force in order to overcome the friction forces acting against it and increase its acceleration.

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