Coefficients Of Friction

October 13,2005

FOCUS

The purpose of this experiment is to examine the coefficients of Friction, both static and kinetic. Friction is the force that exists between one surface and another. There are two types of friction both of which were examined in this experiment, kinetic and static. This lab applied Newton's three laws of motion to find the affects of mass and acceleration to find the force of the wood block and plane. After finding the normal force and the frictional forces the coefficients of friction were found. The angle of repose was used in this experiment to assist in finding the coefficient of static friction.

Essential Definitions

Friction (Force of Friction)-force that is created whenever two surfaces move or try to move across each other.

Angle of Repose- maximum angle at which an object will retain its position with out sliding on an inclined plane.

Kinetic Friction-force holding back regular motion

Static Friction-force that holds back a stationary object up to the point that it just starts moving

Kinetic Coefficient Friction-force restricting the movement of an object that is sliding on a relatively smooth, hard surface

Static Coefficient Friction-force restricting the movement of an object that is stationary on a relatively smooth, hard surface.

DISCUSSION

Newton's three laws of motion applies to this lab in reference to the manner in which the quantities interact. In order to find coefficients of friction we must find the normal force of friction. Friction is a force that affects motion; it acts on objects that are in contact, yet in the opposite direction of motion. Force can be found using Newton's Second Law of motion states the relationship between an object's mass m, its acceleration a, and the applied force F is F = ma. Two factors influence the amount of friction needed; they include the makeup of the objects in contact, such as surface condition, and the amount of force binding the surfaces. It is important to understand that friction is parallel to the surface contact and is only within the space of the area in contact. Newton's First Law of Inertia comes into play during this search to find the coefficients of friction as well. The law states that if no net force acting on an object, it will continue in its state of rest or will continue moving along a straight line with uniform velocity. There is a linear relationship between the force of friction on an object and the normal force on the object used in conjunction with Newton's 1st Law the coefficient of friction may be determined.

The experiment found the amount of friction between the wooden block and the wooden board that it was sliding across. The angle of repose also helped in calculating the coefficient of static friction. The level of friction that different materials exhibit is measured by the coefficient of friction. The formula is µ = Ff /Fn, where µ is the coefficient of friction, Ff is the amount of force that resists motion, frictional force, and Fn is the normal force. Normal force is the force at which one surface is being pushed into another. In the prior experiment we learned that f is equal to the force of tension, T. This is important in this experiment because the force tension is used in place of frictional force to find the coefficients of friction.

RESULTS

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