Laporan unit 2

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Laporan unit 2

  1. 1. FRICTION FORCE Nurul Qalbi Fadilah 1, Nurfajrina Mutmainnah 2, Muh Nurul Kamal Purnama 3, A.Sriatu Nurdianti Departement of Chemistry, FMIPA State University of Makassar 2013 Abstract. Have done experiment about friction force. The Purpose of experiment to (1) understand the factors that influenced friction force, (2) understand concept of static and kinetic friction, and (3) determine the coefficient of static and kinetic friction. Data obtained by using tools spring balance,table pulley,rough beam,smooth beam,rope/yarn,load,foundation board,incline plan,square beam,stopwatch,meter. First activity,observed attraction force of state object.second activity,find the relationship between normal force to friction force.third activity, find relationship between state of surface friction.fourth activity,determine coefficient of static friction on incline. Fifth activity, determine coefficient of kinetic friction inclined plane.Collect data on activities first to third activities that looked basically same tensile force on object is at montionless, ready to move and regular rectilinear motion only on activities that differentiate beams 1 and 3 used same mass but also activities 3 use two different types of surfaces, activities 2 use same type of surface and different normal force. While, activity 4 determine critical angle of objects with different gravity, activitiy 5 determine travel time by different mileage. So,conclusion of this practicum is frictional force is affected by normal force, coefficient of friction, critical angle, and type of surface. KEYWORDS: Friction force, static friction force, kinetic friction force, normal force, coefficient static friction,coefficient kinetic friction, condition object : montionless, ready to move, regular rectilinear motion. PREFACE Did you ever ride a bike ? If you have not , try it . What do you feel when riding a bike ? Why bike can move ? Is a moving bicycle can be stopped ? How do you stop it ? Encouragement , stroke , kick , pull , or other things that cause objects to move or stop the movement of the so-called style . In physics , force is defined as an impulse or a pull . If we pay attention to the movements of objects , such as speeding and stopping the bike , changing the direction of the ball for a kick , and the enlargement of the surface of the inflated balloon , it can be concluded that the force exerted on an object can cause changes in the body according to the force applied. If you pay attention to these forces, whether the source object given the force and force is always in contact? Yes, some styles can occur without a touch of force between the source and the object is given the force. This is the nature of the underlying force grouping into a force touch and don’t touch force. Touch force is a force act on an object with point on the surface of the object. friction force including tap force that appears if the surface of the two objects come into contact physically. Toward the direction of the friction surface and the touch area with a tendency toward motion whether it is motionless, ready to move, or regular rectilinear motion. If we look the statement above , there is a question why the frictional force influenced the state of objects at montionless, ready to move, and regular rectilinear motion? So the answer of these questions are at that time, the object who is montionless there’s no frictional force because the force that occurs of the object is very small objects then when the thing would be regular, the object will undergo static frictional force because the force that occurs on the object is large enough that the object is regular or the force act on an object is equal to the frictional force occurs, and when the object regular rectilinear, motion object has kinetic frictional force because the force that applied is greater than frictional force that occurs so that the object is regular rectilinear motion.
  2. 2. Then the next question is what is the formula to determine the static and kinetic coefficient of friction? The answer to the question which is to determine the formula of the static friction coefficient using the formula (1) and to determine the formula of the kinetic friction coefficient using the formula (2). The classic rules of sliding friction were discovered by Leonardo da Vinci (14521519), but remained unpublished in his notebooks. They were rediscovered by Guillaume Amontons (1699). Amontons presented the nature of friction in terms of surface irregularities and the force required to raise the weight pressing the surfaces together. This view was further elaborated by Belidor (representation of rough surfaces with spherical asperities, 1737) and Leonhard Euler (1750), who derived the angle of repose of a weight on an inclined plane and first distinguished between static and kinetic friction. A different explanation was provided by Desaguliers (1725), who Demonstrated strong cohesion forces between the spheres of roomates lead a small cap is cut off and roomates were then brought into contact with each other. The understanding of friction was further developed by Charles-Augustin de Coulomb (1785). Coulomb Investigated the influence of four factors on friction play: the nature of the materials in contact and their surface coatings; the extent of the surface area; the normal pressure (or load), and the length of time that the surfaces remained in contact ( time of repose). Coulomb Considered further the influence of sliding velocity, temperature and humidity, in order to decide between the different Explanations on the nature of the friction that had been proposed. The distinction between static and dynamic friction is made in Coulomb's friction law (see below), although this distinction was already drawn by Johann Andreas von Segner in 1758. The effect of the time of repose was explained by Musschenbroek (1762) by considering the surfaces of fibrous materials, with fibers meshing together, roomates takes a finite time in the friction increases roomates. John Leslie (1766-1832) Noted a weakness in the views of Amontons and Coulomb. If friction arises from a weight being drawn up the inclined plane of successive asperities, then why is not it balanced through descending the opposite slope? Equally Leslie was skeptical about the role of adhesion proposed by Desaguliers, roomates should on the whole have the same tendency to Accelerate as to retard the motion. In his view friction should be seen as a time-dependent process of flattening, pressing down asperities, roomates creates new obstacles in what were cavities before. Arthur Morrin (1833) developed the concept of sliding versus rolling friction. Osborne Reynolds (1866) derived the equation of viscous flow. This completed the classic empirical models of friction (static, kinetic, and fluid) commonly used today in engineering. The focus of research during the last century has been to understand the physical Mechanisms behind friction. F. Phillip Bowden and David Tabor (1950) Showed that at a microscopic level, the actual area of contact between surfaces is a very small fraction of the apparent area. This actual area of contact, by the caused by " asperities "(roughness) increases with pressure, explaining the proportionality between normal force and frictional force. The development of the atomic force microscope (1986) has recently enabled Scientists to study friction at the atomic scale[1].
  3. 3. At the time this trial is the friction experiments. The purpose of the implementation of this experiment was to determine the factors that affect the friction force, understand the concept of static and kinetic friction and determine the static and kinetic coefficient of friction. In the practicum, there are five methods of frictional force performed. Who first observed the tensile force of the state of the object by using the same beam mass to determine the tensile force on the object when the object was montionless, ready to move, and regular rectilinear motion. Second looked at the relationship between the normal force to the friction force is the same surface normal but different force to determine tensile force on the object is at montionless, ready to move and regular rectilinear motion.Similarly, the second practicum, the practicum looked at the relationship between the state of the three surfaces with a friction force observed gravity objects at rest, ready to regular, and regular rectilinear motion but the type of surface used the refined and coarse surfaces. In the fourth practicum, determine the coefficient of static friction on an inclined plane to calculate the critical angle of objects to determine in advance determine the gravity of objects. And on the fifth practicum, which determine the coefficient of kinetic friction on an inclined plane by first determining the distance that must be traversed by the beam / objects to calculate the travel time required to get to the end object of the incline with a stopwatch. THEORY Friction force is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. Friction force includes a stylish touch , which appears when two surfaces come into contact physical objects . Direction of the force of friction with the surface of the touch pad in the direction opposite to the trend and direction of motion. Friction is the force directed against the motion or tendency toward the object will move. Friction occurs when two objects come into contact. The objects in question here does not have to be solid, but can also be a liquid, or gas. Friction between two solid objects such is the static and kinetic friction, while the force between solids and liquids and gases is the Stokes force. Picture 1. Frictional force (Ff) of a moving object over a surface board There are two types of friction between two solid objects moving straight to each other, the force of static friction and kinetic friction, which distinguished between the touch points between the two surfaces is fixed or mutual change (shift). Static friction is friction
  4. 4. between two solid objects that are not moving relative to each other. Coefficient of static friction is generally denoted byμs, and are generally larger than the coefficient of kinetic friction. Static friction force generated from a force that is applied just before the object is moving. The maximum frictional force between two surfaces before movement is the result of the static friction coefficient multiplied by the normal force. When no movement occurs, the frictional force can have a value of zero to the maximum frictional force. Each style is smaller than the maximum frictional forces trying to move one of the objects will be resisted by the friction force equal to the force is large, but in the opposite direction. Every style that is greater than the maximum frictional force will cause the movement occurs.Once movement occurs , static friction force can no longer be used to describe the kinetics of objects, making use of kinetic friction. Kinetic friction ( or dynamic ) occurs when two objects move relative to each other and rub against each other. Coefficient of kinetic friction is generally denoted by μk and are generally always smaller than the static friction for the same materials Friction is the accumulation of micro interactions between the two surfaces that are touching each other. Styles that work include the electrostatic forces on each surface. First believed that the smooth surface will cause friction (or rather the friction coefficient) becomes smaller value compared with a rough surface, but today is no longer the case. Construction of micro (nano to be exact) on the surface of an object can cause friction to a minimum, even liquids can no longer to be wet In general, the friction force can be written as a series expansion, such as : , f the friction force direction opposite to the force F causes , and apply : 1. For the price o F <fsthen beam itmontionless. 2. For the price F = fsthen the beamprecise to move. 3. If phase enlarged so that F >fsthe moving objects and static friction forcefswill turn into kinetic frictional forcefk. Friction force between two surfaces mutually silent one against the other so-called static friction . The maximum static friction force is equal to the smallest force needed to begin moving object . Once motion has begun , the friction force between two surfaces is usually reduced so a smaller force is needed to keep things moving irregularly . Force acting between the two surfaces move relative to each other is called kinetic friction . If the big statesfsthe maximum force of static friction , then : s fs N (1.1) With s is the coefficient of static friction and the normal force N is large . If the big states fkkinetic frictional force , then :
  5. 5. fk N k with k (1.2) iscoefficient of kinetic friction. When an object is at rest on a flat surface , and then place the object plane is tilted slowly to an angle right to object to the move, the coefficient of static friction between the object and the field is given by the equation , S = tan (1.3) c With cis the angle at the right things will move , called the critical angle . Coefficient of static friction is the tangent value of the angle of the field , with the appropriate state object will move / slide . At angles greater than c , uniformly accelerated beam sliding into the lower end of the inclined plane with acceleration: ax g (sin k cos ) (1.4) where is the angle of the field and k is the coefficient of kinetic friction between the object plane.By measuring the acceleration ax, so coefficient of friction kcan be measured. EXPERIMENTAL METHODOLOGY Before do practicum of friction force ,we need prepare necessary equipment and material in the practicum. The equipment and material are 0-5 N spring balance, pulley table, the beam has two surfaces with a surface that is coarse and refined surfaces, weight 50 grams and 100 grams, string / yarn, board basis, inclined plane, which has a square beam with connective stecker, stopwacth, and gauges as well as writing equipment. the variables identified in this practicum. At first activities practicum observing tensile force of the state of objects, while the variable object manipulation is object then the variable response of these activities and the tensile force control variable is the mass of the beam. Operational definition of variables 1 praktium activities that manipulation of state variables of objects that always be changed from a state of montionless, precise to move and uniform line motion impact on the response variable gravities constant changes of 0.5, 1.6 and 1 , 2 and the control variables are fixed with the beam of mass 1.9 N.In the practicum activities 2 which looked at the relationship between the normal force with friction , variable object manipulation is the normal force and the state of objects then this activity is the response variable tensile force objects and variables that control the type of surface used . Operational definition of the variable activity 2 state manipulation of objects at montionless then precise to move and uniform line motiom , normal force object further changed by adding to the burden on the body with a load of 50 grams , 100 grams and 150 grams so the normal force of the object different , ie the manipulated variable gravity objects will change but , tensile force on the object stationary object remains the same object then a tensile force on the state of precise to move and uniform line motion has increased every change of the normal force of the object , and the control variables type of surface used is slippery surfaces.In the practicum activities 3 that looked at the relationship between the state of the surface friction conditions, variable manipulation is a type of surface and the state of objects, the response variable tensile force objects and variable control of this activity is the normal force object. Operational definition of the variable activity 3 the manipulation variable surface types interchangeable with each measurement done with 2 types of surface used is a coarse surface and refined surface and the state of the object at montionless precise to move then and
  6. 6. uniform line motion, then control variables the normal force on the first object must be weighed with a weight of 1.9 N.In the practicum activities 4 to determine the coefficient of static friction on an inclined plane, variable manipulation is gravity, the response variable is the critical angle and the control variable is the incline. Operational definition of variables 4 activity, variable gravity object manipulation is used without the addition of the load, and the added burden of 50 grams, 100 grams and 150 grams, the response variable critical angle undergo constant change with increasing gravity of the object and control variables was inclined plane using a bow.In the practicum activity 5 to determine the coefficient of kinetic friction on the incline, while the manipulation is variable distance traveled, this activity is the response variable of time traveled to the control variable load mass and the angle of the field. Operational definition of variables 5 activities, the manipulated variable is the distance traveled used from a distance of 70 cm, 90 cm, and 110 cm with of time traveled of the response variable objects constant increase distance traveled each object, and the control variables are used the load mass 1, 1 N and the angle of the field with an angle of 30 º. The working procedures of each practicum activities. Work procedures practicum activity 1, things that must be done, namely provide beams, rope / yarn, spring balance, and subsequently pulley rope all equipment that have been provided and place it on a table that has a flat surface. First weighed the mass of objects / beams are used, then slowly pull the spring with a small force to the object / beam was montionless spring balance and record the appointment on the observation table, then slowly pull the spring until it is the precise to move thing to move further appeal spring back slowly until the beam uniform line motion and recorded appointing straight spring in the table of observations. Work procedure for practicum activity 2 , which need to be prepared are the same equipment in activity 1 but added weight 50 grams and 100 grams and do not forget to weighed beam along a predetermined load, and then assemble the equipment and the added weight above 50 grams the next beam slowly pull spring with state montionless objects, precise to move until uniform line motion and recorded appointing each spring every situation, they change the observation, but repeat it loads on beams replaced ditambahan menjadi100 grams and 150 grams then record the results of the appointment of the spring in the table of observations. Work procedure for practicum activity 3, it needs to be prepared before doing practicum beam with two coarse surfaces and the surface refined, spring balance, the pulley, the next cluster tool into one. First use a beam with a refined surface beam, pull spring slowly starts from the state of the object was montionless, precise to move until uniform line motion and record the results in the table designation spring observations, the same thing is done on the coarse surface of the beam. work procedure on the practicum activity 4, as for the things that need to be prepared that the inclined plane is equipped with a bow, beam / objects, weight 50 grams, 100 grams and 150 grams. Then assembles all of these tools into one entity, then beam that does not put added strain on one end of the field, then gently lift the tip area of a square beam is increased so that the angle of inclination objects and record exactly when the object precise to move in the observation table . The same is done on the beam that has been added burden of 50 grams, 100 grams and 150 grams. At practicum activity 5, equipment used in the activities of 4 is basically the same but the additional load is not used in this activity simply using a fixed mass load, the bar and use stopwacth. Then adjust the angle of the field with an angle greater than the critical angle obtained in section 1 above for a square beam with no additional load and record the slope angle and adjust the distance / length of track to be traversed beam of 70 cm, 90 cm and 110
  7. 7. cm.Further putting a square block at the upper end of the known length of the field in advance of the starting length of 70 cm and release along with running stopwacth beam to measure the of time traveled a square beam moves uniformly accelerated up to the lower end of the field and record the of time traveled on the observation table . Do the same at a distance of 90 cm and 110 cm and record the of time traveled it takes the beam to get to the lower end of the field. EXPERIMENTAL RESULTS DAN DATA ANALYSIS 1. EXPERIMENTAL RESULTS A. Activity 1 Mass of beam = Least scale of spring balance Mass = 10 m= 10 = 5 N = 0,1 N= 0,1 = 0,05 Table1.1Observation result of influence the pull force toward an object No Pull Force (N) Object Condition Montionless 1 ready to move 2 Regular Rectilinear motion 3 A. Activity 2 Kind of the surface is refined Table 1.2.Relation between pull force with normal force Pull Force (N) Normal Force No Object Condition (N) Measure Montionless ready to move 1. 1 2. 3. Average
  8. 8. Regular Rectilinear motion 1. 2. 3. Montionless ready to move 1. 2. 3. 2 Regular rectilinear motion 1. 2. 3. Montionless ready to move 1. 2. 3. 3 Regular rectilinear motion 1. 2. 3. B. Activity3 Normal Froce = Table1.3. Relation between kind of surfacewithPull force Kind of Surface Condition Pull Force (N) Object Montionless I Measure Average
  9. 9. ready to move 1. 2. Refined 3. Regular rectilinear motion 1. 2. 3. Montionless II Precise to move 1. 2. 3. Coarse Uniform line motion 1. 2. 3. C. Activity 4 = 1o/scale Table 1.4. Static friction force at the aslant area. = 1o = 0,5o/scale Critical Angle (0) Weight force No (N) Measure Average o 1. o 2 2. o 3. 1 o 1. o o
  10. 10. 2. o 3. o 1. o 2. o 3. o 1. o 2. o 3. o o 3 o 4 D. Activity 5 Mass of load = Least scale of stopwatch = 0,1 Declivity of angle area = |30,0 0,50| = 0,05 s/scale Table 1.5. Kinetic friction force at the aslant area. Time (s) No Mileage (cm) Measure 1. 1 2. 3. 1. 2 2. 3. Average
  11. 11. 1. 3 2. 3. B. DATA DAN GRAPHIC ANALYSIS DATAANALYSIS A. The First Activity. 1). Motion less (F < fs) 2). Ready to move (F=fs) 3). Uniform Rectilinear Motion (F=fs) B. The Second Activity 1). Table 1.1. the relation between normal force with the friction force Normal friction (N) Ready to move (Fgs max) Regular rectilinear Motion (Fgk) 1,9 2,8 0,8 2,9 3,2 1,2
  12. 12. 3,5 4,6 1,8 2). Graph 1.1. Relation normal friction with static friction force 140 y = 20x + 61 R² = 1 120 Fgs Max 100 80 60 40 20 0 0 1 2 3 4 Normal friction (N) (4 AB) 3). Graph 1.2. Relation between normal friction and kinetic friction force
  13. 13. 140 y = 20x + 61 R² = 1 120 Fgs Max 100 80 60 40 20 0 0 1 2 Normal friction (N) (4 AB) C. The Third Activity a. Rough surface 1). Static coefficient 2). Kinetic coefficient 0,4 b. Soft surface 3 4
  14. 14. 1). Static coefficient `2). Kinetic coefficient 0,5 D. The Four Activity 1) 2). Table1.2.Relation between beam mass and coefficient of static friction force Mass of beam (N) Coefficient 1,1 2,1 2,1 9,5 2,6 9,6 E. The Last Activity 1). Table 1.3.Relation between distance and time
  15. 15. Distance (cm) Time (s2) 81,0 1,0 101,0 1,2 121,0 1,5 Graph 1.3. Relation between Distance and time 140 y = 20x + 61 R² = 1 Distance (s) 120 100 80 60 40 20 0 0 1 2 Time (t) 2 2 3 4
  16. 16. 2 2). The coefficient of kinetic friction force with equation 3.4 2s= 20t2+61 R2= 1 Dk= 1 x 100% = 100 % RE = 100%- 100 %= 0 DISCUSSION Based on the results of experiments that have done of each activity to observe the activities of the state precise tensile force by observing the tensile force precise at montionless, object to regular, and regular rectilinear motion. it shows that the friction force that occur in only a few precise so that the object remains montionless. the kinetic friction force is caused by tensile force beams that appears from friction with the surface of the table. In the second activity that observe the relationship between the normal force with the frictional force on the state of montionless objects, ready to move and regular rectilnear motion, but at montionless objects do not happen so that data can be compared when the object to ready to regular and regular rectilinear motion. it indicates that if the normal force of the object that the static friction also great because there are forces on the object so large static friction increased by the addition of the normal force. In the other hand, when the state of the object regular rectilinear motion do the kinetic friction that has the addition / expansion of the force that the object was uniform. As with the static friction with normal force that increasingly enlarged the static friction of the object was also increased. in the third activity that observe the relationship between the state of the surface of the friction force on the state of montionless objects, ready to move, and regular rectilinear motion use two types of surfaces are a smooth surface and rough surfaces. On a smooth surface gravities occur in objects / beam is greater than the tensile force occurs on the surface of the rough on the precise two-state object to uniform and uniform line motion it is because the rough surface of the friction forces that pull required smaller so that objects uniform on a refined surface, while friction force is smaller so that the required tensile force greater that the object was uniform. In the graphic the activities can not be made because no comparative data. Then the four activity,that determine the coefficient of static friction on an inclined plane using a different gravity of the beam / load observed critical angle formed. From the experimental results it can be greater the gravity of a beam / object that formed the critical
  17. 17. angle is getting smaller because of the attraction isthe great object due to gravity or sooner reached the end of the incline than the gravity that affect the state of the beam. And the Last activity, which determine the coefficient of kinetic friction on an inclined plane that uses a different distance and angle of the beam remains fixed and the mass. So, the closer of the object tilted required less travel time. There are two kind of friction such as static friction force and kinetic friction force. . Static friction occurs when the object to be regular in the right circumstances occur because the force on an object is equal to the force of friction. Kinetic friction occurs when objects in a state of uniform motion because the object power lines are going to be larger than the friction force experienced by the object / beam. CONCLUSION Friction force is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. Friction force includes a stylish touch , which appears when two surfaces come into contact physical objects . Direction of the force of friction with the surface of the touch pad in the direction opposite to the trend and direction of motion. Friction is the force directed against the motion or tendency toward the object will move. Friction occurs when two objects come into contact. The objects in question here does not have to be solid, but can also be a liquid, or gas. Friction between two solid objects such is the static and kinetic friction, while the force between solids and liquids and gases is the Stokes force. There are two types of friction between two solid objects moving straight to each other, the force of static friction and kinetic friction, which distinguished between the touch points between the two surfaces is fixed or mutual change (shift).Static friction is friction between two solid objects that are not moving relative to each other. Coefficient of static friction is generally denoted by μs, and are generally larger than the coefficient of kinetic friction.Kinetic friction ( or dynamic ) occurs when two objects move relative to each other and rub against each other. Coefficient of kinetic friction is generally denoted by μk and are generally always smaller than the static friction for the same materials. There are two types of friction between two solid objects moving straight to each other, the force of static friction and kinetic friction, which distinguished between the touch points between the two surfaces is fixed or mutual change (shift). Static friction is friction between two solid objects that are not moving relative to each other. Coefficient of static friction is generally denoted byμs, and are generally larger than the coefficient of kinetic friction. Static friction force generated from a force that is applied just before the object is moving. The maximum frictional force between two surfaces before movement is the result of the static friction coefficient multiplied by the normal force. When no movement occurs, the frictional force can have a value of zero to the maximum frictional force. Each style is smaller than the maximum frictional forces trying to move one of the objects will be resisted by the friction force equal to the force is large, but in the opposite direction. Every style that is greater than the maximum frictional force will cause the movement occurs.Once movement occurs , static friction force can no longer be used to describe the kinetics of objects, making use of kinetic friction. Kinetic friction ( or dynamic ) occurs when two objects move relative to each other and rub against each other. Coefficient of kinetic friction
  18. 18. is generally denoted by μk and are generally always smaller than the static friction for the same materials : With cis the angle at the right things will move , called the critical angle . Coefficient of static friction is the tangent value of the angle of the field , with the appropriate state object will move / slide . At angles greater than c , uniformly accelerated beam sliding into the lower end of the inclined plane with acceleration: ax g (sin k cos ) (3) REFERENCES [1] Anonim. 2013. Friction. http://en.wikipedia.org/wiki/Friction. [2]Husna.2011.Laporan praktikum /2011/06/laporan-praktikum-fisika.html. fisika. http://gusnablogspotcom.blogspot.com [3]Septiawan. 2013. Laporan fisika. http://setiawanfiles.blogspot.com/2013/04/laporanfisika.html.

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