TYPES OF FRICTION And how to reduce the force due to friction

Sliding Friction Exists when an object slides across a surface. Exerted by the surface on the object. Also called Kinetic Friction. F frict-sliding = μ frict-sliding F norm

Static Friction Exists when two objects are both at rest relative to each other. Prevents an object from being set in motion. Example: You exert 5N of force on a box resting on a surface, it does not move. You increase the force to 20N. It still does not move. You increase to 26N and the box is finally budged from its position. F frict-static ≤ μ frict-static F norm

Rolling Exists when an object rolls across a surface. It is the force resisting the roll of the object. F frict-rolling = μ frict-rolling F norm

Fluid Friction Exists when an object is moving through a fluid or when a fluid moves over an object. Both air and liquid are considered to be fluids.

Remember! The coefficient of friction is dependent upon the surfaces involved. The greater the coefficient of friction the greater the friction force.

How do we reduce friction? Reduce the coefficient of friction by… Rolling it! When you roll an object instead of sliding it, there is less interaction between surfaces, lowering the force of friction. Using a Lubricant! When you use a lubricant it acts to “smooth” out a surface by filling in imperfections and making each of the surfaces glide. Common lubricants are oil and grease.

Why would friction need to be reduced?