To cause motion, you need to slightly increase m, the hanging mass, by 0. The coefficient of kinetic friction between the puck and ice is 0. Dry friction is subdivided into static friction stiction between nonmoving surfaces, and kinetic friction between moving. Apply the concepts of static and kinetic friction to problems involving constant motion or impending motion.
Experiment 6 the coefficient of friction equipment. Based on the data you enter, if the ratio mm is exactly equal to the selected. To determine the coefficient of kinetic friction between two selected surfaces by using a horizontal surface. Th is means that in a race from a standing start without starting blocks figure 6, you ideally want to push backwards with both feet, making. As p increases, static friction force f increases as well until it reaches a maximum value f m. Standard test method for static and kinetic coefficients of friction of plastic film and sheeting iso 8295 plasticsfilm and sheetingdetermination of the coefficients of friction other models available 322500 incline plane coefficient of friction tester. Emerging nvestigators redesigning an experiment to. Kinetic friction once the force applied on a mass exceeds fs,max and the mass begins to move, a kinetic friction force, fk, exists. Kinetic friction definition, types, examples, questions. Coefficients of static and kinetic friction of uncoated writing tappi. Coefficient of static friction slide angle of packaging. For the second graph, input the average kinetic friction in column b.
Pdf measuring the coefficient of kinetic friction is much more difficult than that of the static counterpart. Friction is the force that resists the relative motion of one surface. Specify the range of f such that the block stays at rest. A physics class consisting of six lab groups wants to test the hypothesis that the coefficient of static friction between the board and the block equals the coefficient of kinetic friction between the board and the block.
Example friction force the friction force of a 100 lb wooden crate pushed across a concrete floor with friction. Kinetic frictional coefficients are used with relative motion between objects. Frictional force f ma f 4m n coefficient of kinetic friction 4mmg 4g 0. Friction is the force that resists the relative motion of one surface in contact with another surface. This method describes a horizontal plane procedure for the determination of the coefficient of static and kinetic friction of paper measured when sliding against. Some of the worksheets below are coefficient of friction problems worksheet with answers, several calculations involving coefficient of friction, types of friction like rolling friction, sliding friction, fluid friction, static and kinetic friction. The socalled friction, or timoshenko, oscillator consists of a plate set into periodic motion through the competition between gravity and friction on its rotating supports.
Kinetic friction and static friction physics problems. Define and calculate the coefficients of kinetic and static friction, and give the relationship of friction to the normal force. In this lab, you will measure the coefficients of friction between the block and a wooden board. By measuring the length of the sloped board l and the heights, h 1 and h 2, as well as d, the horizontal distance that the block falls, we were able to calculate the coefficient of kinetic friction for the wooden surfaces by using a fortran90 program. No units dimensionless depends on both surfaces doesnt depend on size of contact area usually. If the coefficient of static friction is ms, calculate the force required to move the box. Usually, kinetic friction is less than the maximum value of static friction. We employed an inclined plane, the tool for measuring time, and a protractor. To measure the coefficients of static and kinetic friction between a wooden block and a wooden plane. On the other hand, fx, called the coefficient of kinetic or sliding friction, is the value of the.
A body moving on the surface experiences a force in the opposite direction of its movement. Our prototype is mainly composed of a motor, lego blocks, and a. Now you want to find the coefficient of kinetic friction. Note that static coefficients are somewhat higher than the kinetic or sliding coefficients. A wooden block, an inclined plane with pulley, cord, weights, a protractor, a balance, and a meter stick. Dry friction is a force that opposes the relative lateral motion of two solid surfaces in contact. The friction coefficient between the object and the surface is 0. Coefficient of friction of paper used in a copy machine. Fm psn further increase in p causes the block to begin to move as f drops to a smaller kinetic friction force f k. Kinetic coefficient an overview sciencedirect topics. Difference between kinetic friction and static friction. Unlike the static friction force, the kinetic friction force does not change in magnitude. A computer with internet connection, a calculator the builtin calculator of the computer may be used. The force required to move the load is recorded and the coefficient of kinetic friction is calculated.
To measure the coefficient of static and kinetic friction between a block and an inclined plane and to examine the relationship between the planes angle and its mechanical efficiency. A physics 1 student applies a force f at angle q on a box of mass m on a floor. When a force is applied to a body resting on a rough plane so that the body moves or tends to move, a frictional force acts on the body in opposition to the applied force. Standard test method for static and kinetic coefficients of friction of plastic film and sheeting1 this standard is issued under the. Kinetic friction is defined as a force that acts between moving surfaces. Both static and kinetic friction depend on the surfaces of the box and the floor, and on how hard the box and floor are pressed together. Summary of method one specimen of the paper sample is clamped to a horizont al plane surface, the other to a specimen sled.
The coefficient of kinetic friction is the ratio fw or mgmg, or simply mm. Coefficient of friction problems worksheet with answers. For any specific application the ideal method of determining the coefficient of friction is by trials. A skater with mass 58 kg is holding one end of a rope and standing at rest on ice. Friction is easily defined as the force that holds back a sliding object. Coefficient of friction extreme care is needed in using friction coefficients and additional independent references should be used. Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. Example friction force a 100 lb wooden crate is pushed across a concrete floor. A wooden block weighs 100 n, and is sliding to the right on a smooth horizontal concrete surface at a speed of 5 ms.
The strength of friction between two static surfaces can be estimated by calculating the coefficient of static friction. The period of such an oscillator gives a measurement of the coefficient of kinetic friction. When pulling horizontally on a level surface, the normal force is the total weight mg of the block plus any added mass. Standard test method for static and kinetic coefficients. Kinetic friction is high for rough and dry surfaces and low for wet and smooth ones. The coefficient for the static variety is generally higher than the kinetic friction coefficient for two solid surfaces, in. Thus, the static coefficient of friction concerns the force restricting the movement of an object that is stationary on a relatively smooth, hard surface. Pdf minimal tools for accurately measuring the coefficient of.
Lecture 8, pg 10 an experiment two blocks are connected on the table as shown. Coefficients of static and kinetic friction of uncoated. The proportionality constant is called the coefficient of static friction. When one body lies at rest on a surface and an attempt is made to push it, another type of friction, static friction. Static coefficients are somewhat higher than kinetic coefficients. Determine the force of friction acting on the box if a horizontal external applied force is exerted on it of magnitude. Friction and coefficients of friction nathan sandberg. Coefficient of friction dry greasy test method static sliding static sliding aluminum aluminum 1,051,35 1,4 0,3 aluminum mild steel 0,61 0,47 brake material cast iron 0,4 brake material cast iron wet 0,2 brass cast iron 0,3 brick wood 0,6. Determine whether the block is in equilibrium and find the value of the friction force. Once an object is in motion, the friction force changes to kinetic friction force, which is proportional to the magnitude of normal force, fk mk n. Static frictional coefficients are used for objects without relative motion.
A coefficient of friction cof test was recommended to measure the static and kinetic coefficients of friction between two sheets of paper. Find the slope which equals the coefficient of static friction and record it on your data sheet. The magnitude of the force will depend on the coefficient of kinetic friction between the two material. Coefficient of kinetic friction is given by the equation. Minimal tools for accurately measuring the coefficient of kinetic. These laws are generally true, but there are exceptions.
If maximum friction force is less than friction force required for equilibrium, block will slide. All frictional forces is dependent on the normal of the object. The average kinetic friction coefficients and their standard. There are no national standards or requirements for the coefficient of friction for walking surfaces, though local municipalities may carry specific requirements through building codes. When friction is strong enough to prevent an object from moving, we call it static friction. The kinetic friction force is generally lower than the static one, so that one needs to define two friction coefficients, the static coefficient. Coefficient of friction material 1 material 2 dry greasy. Friction can thought of as a force that opposes motion. The kinetic friction force is a constant value that depends on the interaction between the horizontal surface and the object. Once you overcome static friction, kinetic friction is the force holding back regular motion. Kinetic friction coefficients are generally less than static friction coefficients, which is the reason that it is much easier to keep a heavy object in motion than it. The coefficient of friction is defined as the ratio of force of friction to the. Coefficient of friction of paper used in a copy machine application report introduction a manufacturer of copy paper needs to investigate the cause of copy machine failure as a result of frequent paper jams. Kinetic friction is sometimes referred to as sliding friction.
158 1269 1295 146 288 89 916 1507 299 37 1306 288 1410 708 1414 1485 398 1472 1563 1013 481 733 1405 726 71 1367 585 437 979 1126 1299 36 1068 857 1487 191 1513 1367 1074 281 1090 359 1436 207 258 48 845 991 472