friction

• friction is a motion that occurs when two surface rub against each other
• kinetic friction is the force between moving objects, it opposes their motion
• the force of friction always acts opposite to the direction of movement or attempted movement
• static friction is the force that oppose the motion of an object when it is stationary
• rolling friction is when the object is moving and the surface is stationary,the friction is the same as he surface is moving
• fluid friction is the friction between the fluid and the surface of the object