A force that is opposite to the direction of motion is friction. Friction can be kinetic or static. Kinetic friction acts on a moving object, while static friction acts on a stationary object.Continue Reading
The direction of static friction is unclear. A method used to determine its direction is by observing whether an object moves in the absence of friction. If it moves, friction is in the opposite direction. If it does not, friction is zero.
The force that doesn't allow relative motion between two objects that are in contact with each other is called friction. At times, it can be useful, for example, when it keeps a person from falling while running or walking. It also ensures that a car doesn't skid during driving under normal conditions.Learn more about Motion & Mechanics