Frictioin Force Report by Fildia Putri

111Equation Chapter 1 Section 1FRICTION FORCE

Fildia Putri, Rafika Sri Rahayu , Nul Lailah , Nurul Wisna Afianti, Nur Rahmah

Marisa Raden.

Departement of Chemistry, FMIPA State University of Makassar 2013

Abstract. Have done the experiment with title friction force. Purpose experiments to identify factors that affect friction force, understand concept of static and kinetic friction, and determine the coefficient of static and kinetic friction. Data obtained by using tools a pulley, rope/yarn, spring balance, refined and coarse beams, board basis, inclined plane, stopwatch, meter, and a square beam. First activities observed drag force against state object, activity 2 relationship between normal force to friction force, activity 3 relationship between state of surface friction, activity 4 determine coefficient of static friction on incline, activity 5 determine coefficient of kinetic friction inclined plane. Collecting data on activities of first to third activities that looked basically same tensile force on object is at montionless, precise to move and uniform line 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 activities 4 determine critical angle of objects with different gravity, activities 5 determine travel time by different mileage. So, conclusion of this practicum is frictional force affected by normal force, coefficient of friction, critical angle, and type of surface.

KEYWORDS: Friction force, article format, static friction force, kinetic friction force, normal force, coefficient static friction, coefficient kinetic friction, condition object : montionless, preciseto move, uniform line motion.

INTRODUCTION

In our daily activity we often find the application of frictional force. Two objects that are touching each other which can cause it to rub against objects. Usually friction between two surfaces that are touching each good in the air, water or solid objects. Friction can be known through experiments with doing pengekuran. Calculate the frictional force can be done by various methods, one of which is using a spring balance, pulley, beam by calculating the tensile force keaadan object against some good things in is at montionless, precise to uniform, and uniform line motion. hen, using two different types of surface that is refined surface and a smooth surface by calculating the tensile strength of the object at rest, precise to uniform and uniform line which produces motion speed difference. In addition to these methods, using the incline as the testers are used to calculate the friction coefficient of friction coefficient of frictional force either static or kinetic frictional force coefficient which has a value of critical angle and distance, as well as a stopwatch to calculate the travel time object / beam to reach the end inclined plane.

Based on the above statement there is a question why the frictional force influenced the state of objects at montionless, precise to uniform, and uniform line

regular ?. Answers to these questions are due at the time the object was montionless objects do not experience frictional force because the force that occurs in a very small objects or even no, continue when the precise thing would be uniform the object will undergo static frictional force due to the force exerted on the object is large enough that the object was uniform or the force exerted on an object is equal to the frictional force occurs, and when the object uniform line motion objects having kinetic frictional force due to the force applied is greater than frictional force that occur so that the object was uniform motion line.

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).

μs=f s

N……… ..(1)

μk=f k

N……….(2)The classic rules of sliding friction were discovered

by Leonardo da Vinci (1452-1519), 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].

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, precise to move, and uniform line 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, precise to move and uniform line 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, precise to uniform, and uniform line 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[2]. 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.

Frictional force at work when things move in the air , water , or glide over other solid objects . For objects moving through the air , the air friction force on an

object depends on the size of objects that come into contact with air . The greater the bandwidth is greater touch of air friction force on the object . This concept is used by the jumpers. When an object moves through the air , the surface of the object will be in contact with air , causing friction between the object with air . Similarly, when moving in the water. Friction force is also always occurs between the contact surfaces of solid objects , even if the object is very slippery .Very slippery surfaces is actually very rough on a microscopic scale . When we try to move an object , this miskroskopis protrusions interfere with the motion . In addition , at the atomic level (remember that all matter is made of atoms) , a bulge on the surface causes the atoms are very close to the other surface , so that the electric forces between atoms can form chemical bonds , as a unifying small among two moving surfaces . When a moving object , for example when we push a book on a table surface , the movement of the book have problems and eventually stop , because there is friction between the bottom surface of the book with a table surface and the friction between the surface of the book with the air , where the scale miskropis , this occurs due to the formation and release of the bond . If the surface of an object with surfaces rub against each other ,each of these objects do frictional force between each other[3].

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 μ s, 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[4].

A block is pushed on the table will move When a beam mass m, we remove the initial velocity Vo on a horizontal plane , then the beam will eventually stop . This means that in the beam movement slowed , or there is a force that holds the beam , this style is called friction. The magnitude of the frictional force is determined by the coefficient of friction between the two surfaces of the objects and the normal force . The coefficient of friction is determined by the surface roughness and objects.

Friction force divided into two : the static friction (fs) and kinetic friction (fk). A block of weight W, is the rough horizontal plane , then pulled by force F as in Image 1.1 below.

f the friction force direction opposite to the force F causes , and apply :

1. For the price o F < fs then beam it montionless.

2. For the price F = fs then the beam precise to move.

3. If phase enlarged so that F > fs the moving objects and static friction force fs will turn into kinetic frictional force fk.

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 states fs the maximum force of static friction , then :

μs=f s

N(1.1)

With

μs

is the coefficient of static friction and the normal force N is large . If the big

states fk kinetic frictional force , then :

μk=f k

N(1.2)

with

μk

is coefficient 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 c (1.3)

With c is 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:

Image 1.1: The forces acting on the object.

W

N

fF

ax = g (sin θ − μk cos θ )(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 k can be measured.

EKSPERIMENTAL METHODOLOGY

Before doing practicum of friction force we first 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.

Furthermore, the variables identified in this practicum. At first activities practicum observing tensile force of the state of objects, while the variable object manipulation is objec 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 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 procedures 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 procedures for practicum activities 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.

Furthermore, work procedure on the practicum activities 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 activities 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 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.

EKSPERIMENTAL RESULTS DAN DATA ANALYSIS

1. EKSPERIMENTAL RESULTSA. Activity 1

Mass of beam = ¿190 ±5∨gLeast scale of spring balance

Mass = 10 g/ scale ∆m = 12

× 10 = 5 g/ scale

N = 0,1 N / scale ∆N = 12

× 0,1 = 0,05 N / scale

Table 1.1 Observation result of influence the pull force toward an object

No Pull Force (N) Object Condition

1 ¿1,50 ± 0,05∨N Montionless

2 ¿1,80 ± 0,05∨N Precise to move

3 ¿0,80 ± 0,05∨N Uniform line motion

B. Activity 2Kind of the surface is refinedTable 1.2.Relation between pull force with normal force

No

Normal Force

(N)

Object Condition

Pull Force (N)

Measure Average

1 ¿2,190 ± 0,05∨NMontionless ¿1,50 ± 0,05∨N ¿1,50 ± 0,05∨N

Precise to move 1. ¿1,80 ± 0,05∨N

2.¿1,60 ± 0,05∨N

3.¿1,80 ± 0,05∨N

¿1,73 ± 0,05∨N

Uniform line motion

1.¿0,80 ± 0,05∨N

2.¿0,90 ± 0,05∨N

3.¿0,90 ± 0,05∨N

¿0,87 ± 0,05∨N

2 ¿2,90 ± 0,05∨N

Montionless ¿2,00 ± 0,05∨N ¿2,00 ± 0,05∨N

Precise to move 1. ¿2,00 ± 0,05∨N

2.¿2,00 ± 0,05∨N

3.¿2,40 ± 0,05∨N

¿2,13 ± 0,05∨N

Uniform line motion

1.¿1,20 ± 0,050∨N

2.¿1,10 ± 0,050∨N

3.¿1,20 ± 0,050∨N

¿1,17 ± 0,05∨N

3 ¿3,40 ± 0,05∨N

Montionless ¿0,50 ± 0,05∨N ¿2,30 ± 0,05∨N

Precise to move 1.¿2,60 ± 0,05∨N

2.¿2,80 ± 0,05∨N

3.¿2,90 ± 0,05∨N

¿2,77 ± 0,05∨N

Uniform line motion

1.¿2,40 ± 0,05∨N

2.¿2,30 ± 0,05∨N

3.¿2,20 ± 0,05∨N

¿6,90 ± 0,05∨N

C. Activity 3Normal Froce = ¿1,90 ± 0,05∨NTable 1.3. Relation between kind of surface with Pull force

Kind of

Surface

Object

Condition

Pull Force (N)

Measure Average

I

Refined

Montionless ¿2,30 ± 0,05∨N ¿2,300 ± 0,05∨N

Precise to move 1. ¿2,60 ± 0,05∨N

2.¿2,80 ± 0,05∨N

3.¿2,90 ± 0,05∨N

¿2,77 ± 0,05∨N

Uniform line motion

1.¿2,40 ± 0,05∨N

2.¿2,30 ± 0,05∨N

3.¿2,20 ± 0,05∨N

¿2,30 ± 0,05∨N

II

Coarse

Montionless ¿2,80 ± 0,05∨N ¿2,80 ± 0,05∨N

Precise to move 1.¿3,10 ± 0,05∨N

2.¿3,20 ± 0,05∨N

3.¿3,20 ± 0,05∨N

¿3,17 ± 0,05∨N

Uniform line motion

1.¿1,96 ± 0,05∨N

2.¿1,80 ± 0,05∨N

3.¿1,80 ± 0,05∨N

¿1,83 ± 0,05∨N

D. Activity 4

θ = 1o/scale ∆ θ = 12

× 1o = 0,5o/scale

Table 1.4. Static friction force at the aslant area.

NoWeight force

(N)

Critical Angle (0)

Measure Average

1 ¿1,60 ± 0,05∨N

1. ¿21,0 ± 0,5∨¿o

2.¿20,0 ± 0,5∨¿o

3.¿20,0 ± 0,5∨¿o

¿20,3 ± 0,5∨¿o

2 ¿2,10 ± 0,05∨N

1.¿17,0 ± 0,5∨¿o

2.¿17,0 ± 0,5∨¿o

3.¿16,0 ± 0,5∨¿o

¿16,7 ± 0,5∨¿o

3 ¿2,60 ± 0,05∨N

1.¿16,0 ± 0,5∨¿o

2.¿15,0 ± 0,5∨¿o

3.¿15,0 ± 0,5∨¿o

¿15,30 ± 0,5∨¿o

E. Activity 5Mass of load = ¿110± 5∨g

Least scale of stopwatch = 0,1 s/ scale ∆ t=12

x 0,1 s /scale

Declivity of angle area = |30,0 ± 0,50|° = 0,05 s/scale

Table 1.5. Kinetic friction force at the aslant area.

No Mileage (cm)

Time (s)

Measure Average

1

¿84,00 ± 0,05∨cm 1.¿1,60 ± 0,05∨s

2.¿1,60 ± 0,05∨s

3.¿1,70 ± 0,05∨s

¿1,63 ± 0,05∨s

2

¿104,30 ± 0,05∨cm 1.¿1,90 ± 0,05∨s

2.¿2,00 ± 0,05∨s

3.¿1,90 ± 0,05∨s

¿1,93 ± 0,05∨s

3

¿110,00± 0,05∨cm 1.¿2,30 ± 0,05∨s

2.¿2,20 ± 0,05∨s

3.¿2,30 ± 0,05∨s

¿2,27 ± 0,05∨s

2. DATA DAN GRAPHIC ANALYSISA. Activity 1

1. Images the forces acting on the body when condition the object is at mentionless, precise to move and uniform line motion.

B. Activity 2Table: 2.1. Relationship between the normal force and friction force.

a

F

µk

F

W

N

Image 1. The forces acting on the object (a) mentionless, (b) precise to move, and (c) uniform linemotion.

(c)(b)(a)

μs

F

N

WW

N

Normal Force

(N)

Friction Force

(N)

Static Friction Force (f s ¿

(N)

Kinetic Friction Force f k¿

(N)

¿1,90 ± 0,05∨N ¿1,80 ± 0,05∨¿ ¿0,87 ± 0,05∨¿

¿2,40 ± 0,05∨N ¿2,00 ± 0,05∨¿ ¿1,17 ± 0,05∨¿

¿3,40 ± 0,05∨N 2,60 ± 0,05∨N ¿6,90 ± 0,05∨¿

μs=f s

N

μs1=1,80

1,96=0,92 N

μs2=2,60

2,40=1,08 N

μs3=3,30

3,40=0,97 N

μk=f k

N

μk1=0,87

1,90=0,46 N μk2

=1,172,40

=0,48 N

μk3=6,90

3,40=2,03 N

Table: 2.2. Relationship between the normal force and coefficient of friction force.

Normal Force

(N)

Coefficient of Friction Force

Coefficient Static Friction

(μs ¿

Coefficient Kinetic Friction (μk ¿

¿1,90 ± 0,05∨N 0,92 0,46

¿2,40 ± 0,05∨N 1,08 0,48

¿3,40 ± 0,05∨N 0,76 2,03

For static friction force :

∆ μs=|∆ f s

f s

+ ∆ NN |μs

∆ μs1=|∆ f s1

f s1

+ ∆ NN |μs1

¿|12

x0,1

1,80+

12

x 0,1

1,90 |0,92

¿|0,051,80

+0,051,90|0,92

¿|1,80+0,03|0,92

¿0,05

∆ μs2=|∆ f s2

f s2

+ ∆ NN |μs2

¿|12

x0,1

2,00+

12

x 0,1

2,40 |1,08

¿|0,052,00

+0,052,40|1,08

¿|0,02+0,02|1,08

¿0,043

∆ μs3=|∆ f s3

f s3

+ ∆ NN |μs3

¿|12

x0,1

2,60+

12

x 0,1

3,40 |0,76

¿|0,052,60

+0,053,40|0,76

¿|0,02+0,01|0,76

¿0,228

1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.60

0.5

1

1.5

2

2.5

3

f(x) = 0.542857142857143 x + 0.74R² = 0.991758241758242

Normal Force (N)

Stati

c Fric

tion

Forc

e (N

)

y=mx+c

m= yx

Graphic 1.1.Relationship between the normal force and

static friction force

m=F gs

N→ F gs=N x μs

m=N x μs

N

m=μs

Truth degree

DK=R2 x100 %

¿0,9918 x100 %

¿99,18 %

Relative Error

KR=(100 %−DK )

¿ (100 %−99,18 % )

¿0,82 %

KR=∆ μs

μs

→ ∆ μs=KR x μs

¿0,83 x 0,5429=0,4506

So ,PF=|μs± ∆ μs|=|0,54 ± 0,45|

For kinetic friction force :

∆ μk=|∆ f k

f k

+ ∆ NN |μk

∆ μk1=|∆ f k1

f k1

+ ∆ NN |μk1

¿|12

x0,1

0,87+

12

x 0,1

1,90 |0,46

¿|0,050,87

+ 0,051,90|0,46

¿|0,057+0,03|0,46

¿0,0400

∆ μk2=|∆ f k2

f k2

+ ∆ NN |μk2

¿|12

x0,1

1,70+

12

x 0,1

2,90 |0,59

¿|0,051,70

+0,052,90|0,59

¿|0,029+0,02|0,59

¿0,0289

∆ μk3=|∆ f k3

f k3

+ ∆ NN |μk3

¿|12

x0,1

6,90+

12

x 0,1

3,40 |2,03

¿|0,056,90

+0,053,40|2,03

¿|0,007+0,01|2,03

¿0,0345

1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.60

1

2

3

4

5

6

7

8

f(x) = 4.26428571428571 x − 7.965R² = 0.918605276929301

Normal Force (N)

Kine

tic F

rictio

n Fo

rce

(N)

Graphic 1.2. Relationship between the normal force and

kinetic friction force

y=mx+c

m= yx

m=F gk

N→ F gk=N x μk

m=N x μk

N

m=μk

Truth degree

DK=R2 x100 %

¿0,9186 x100 %

¿91,86 %

Relative Error

KR=(100 %−DK )

¿ (100 %−95,5 % )

¿8,14 %

KR=∆ μk

μk

→ ∆ μk=KR x μk

¿8,14 x 4,2643=34,71

So ,PF=|μk ± ∆ μk|=|4,26 ±34,71|

C. Activity 3Coefficient Friction Force

Coeffient static friction

μs1=

fgs

N=2,77

1,90=1,46

μs2=

fgs

N=3,17

1,90=1,67

Coefficient kinetic friction

μk1=

fgk

N=2,30

1,90=0,68

μk2=

fgk

N=1,83

1,90=0,96

Tabel: 2.3. Relationship between the coefficient of friction force every surface with friction force.

Types of Surface Coefficient of friction force

Coefficient static friction

(μs ¿

Coefficient kinetic friction (μk ¿

IRefined

1,46 1,21

IICoarse

1,67 0,96

Uncertainly

Static Friction Force

δ 1=|2,77−2,66|=0,11 N

δ 2=|2,77−2,80|=0,03 N

δ 3=|2,77−2,90|=0,13 N

δmax=0,13 N

∆ μs1={|∆ f g

f g

+ ∆ NN |}μs1

¿ {|0,132,77

+ 0,051,90|}1,46

¿0,073

Relative Error

KR=∆ μs1

μs1

x100 %

¿ 0,0731,46

x 100 %=5 %

Truth Degree

DK=(100 %−KR )

¿ (100 %−5 % )

¿5 %

so , PF=|μs1± ∆ μs1|=|1,46 ±0,0730|

δ 1=|3,17−3,10|=0,07 N

δ 2=|3,17−3,20|=0,03 N

δ 3=|3,17−3,20|=0,03 N

δmax=0,07 N

∆ μs2={|∆ f g

f g

+ ∆ NN |}μs2

¿ {|0,073,17

+ 0,051,90|}1,67

¿ {|0,05+0,03|}1,67

¿0,134

Relative Error

KR=∆ μs2

μs2

x100 %

¿ 0,1341,67

x 100 %=8,02 %

Truth Degree

DK=(100 %−KR )

¿ (100 %−8,02 % )

¿91,98 %

so , PF=|μs2± ∆ μs2|=|1,67 ±0,134|

Kinetic Friction Force

δ 1=|2,30−2,40|=0,10 N

δ 2=|2,30−2,30|=0 N

δ 3=|2,30−2,20|=0,10 N

δmax=0,10 N

∆ μk1={|∆ f g

f g

+ ∆ NN |}μk1

¿ {|0,102,30

+ 0,051,90|}1,21

¿ {|0,043+0,026|}1,21

¿0,083

Relative Error

KR=∆ μk1

μk1

x 100 %

¿ 0,0750,68

x 100 %=6,86 %

Truth Degree

DK=(100 %−KR )

¿ (100 %−6,86 % )

¿88,97 %

so , PF=|μk1± ∆ μk1|=|1,21± 0,083|

δ 1=|1,83−1,96|=0,13N

δ 2=|1,83−1,80|=0,03N

δ 3=|1,83−1,80|=0,03N

δmax=0,13 N

∆ μk2={|∆ f g

f g

+ ∆ NN |}μk2

¿ {|0,131,83

+ 0,051,90|}0,96

¿ {|0,07+0,03|}0,96

¿0,096

Relative Error

KR=∆ μk2

μk2

x100 %

¿ 0,0960,96

x 100 %=10,00 %

Truth Degree

DK=(100 %−KR )

¿ (100 %−10,00 % )

¿90,00 %

so , PF=|μk2± ∆ μk2|=|0,960 ± 0,0960|

D. Activity 4Coefficient Static Friction

Ʃ F=0

m g sin θ−f g sin θ=0

m g sin θ=f g →f g=μsmaxx N

m g sin θ=μsmaxm gcosθ

μsmax= sinθ

cos θ

¿ tanθ

1. μs1=tan θ=tan 20,3 x

π180

=0,36991

∆ μs1=

δ μs

δθx∆ θ

¿ δ sin θδθ

x ∆ θ

∆ μs1

μs1

= sec2 θtan θ

x ∆ θ

∆ μs1

μs1

= 1cos2θ

xcosθsin θ

x ∆ θ

∆ μs1

μs1

= 112

sin2θx ∆ θ

∆ μs1= 2

sin2θx ∆ θ

∆ μs1= 2

sin220,3x1= 2

0,65077x0,0174=0,0534

Relative Error

KR=∆ μs1

μs1

x100 %=0,05340,3699

x100 %=7,6 %

Truth Degree

DK=100 %−KR=100 %−7,6 %=92,4 %

so , PF=|μs1± ∆ μs1|=|0,37 ± 0,053|

2. μs2=tan θ=tan 16,7 ° x

π180

=0,3000

∆ μs2=

δ μs

δθx∆ θ

¿ δ sin θδθ

x ∆ θ

∆ μs2

μs2

= sec2 θtan θ

x ∆ θ

∆ μs2

μs2

= 1cos2θ

xcosθsin θ

x ∆ θ

∆ μs2

μs2

= 112

sin2θx ∆ θ

∆ μs2= 2

sin2θx ∆ θ

∆ μs2= 2

sin216,7x1= 2

0,5504x 0,0174=0,0632

Relative Error

KR=∆ μs2

μs2

x100 %=0,06320,3000

x 100 %=21,1 %

Truth Degree

DK=100 %−KR=100 %−21,1%=78,9 %

so , PF=|μs2± ∆ μs2|=|0,300 ±0,0632|

3. μs3=tan θ=tan 15,3 ° x

π180

=0,2735

∆ μs3=

δ μs

δθx∆ θ

¿ δ sin θδθ

x ∆ θ

∆ μs3

μs3

= sec 2θtan θ

x ∆ θ

∆ μs3

μs3

= 1cos2θ

xcosθsin θ

x ∆ θ

∆ μs3

μs3

= 112

sin2θx ∆ θ

∆ μs3= 2

sin2θx ∆ θ

∆ μs3= 2

sin2 20x1= 2

0,6429x0,0174=0,0541

Relative Error

KR=∆ μs3

μs3

x100 %=0,06830,2735

x 100 %=24,97 %

Truth Degree

DK=100 %−KR=100 %−24,97 %=75,03 %

so , PF=|μs3± ∆ μs3|=|0,27 ± 0,068|

Tabel: 2.4. Relationship between the mass of load and coefficient static friction.

The Mass of Load

(Gram)

Coefficient of friction force

Coefficient static friction (μk ¿

160 0,3699

210 0,300

260 0,2735

E. Activity 5

80 85 90 95 100 105 110 115 120 125 1300

0.5

1

1.5

2

2.5

f(x) = 0.0159938004649651 x + 0.278378704930463R² = 0.998000670105789

Distance Traveled (cm)

Qua

drat

e of

tim

e tr

avel

ed (s

)

s=12

a t2

tanθ=m= t 2

s

m= t 2

12

a t 2

m=1

12

a=

11a2

=2a

a m=2

a= 2m

= 20,016

=125 cm /s2

Graphic 1.2. Relationship between the quadrate of time

traveled (t2) and distance traveled (s).

Truth Degree

DK=R2 x100 %=0,998 x 100 %=99,8 %

Relative Error

KR=100 %−DR=100 %−99,8%=0,2 %

∆ a=KR x a=0,002 x125=0,25

so , PF=|a ± ∆ a|=|125,0 ± 0,250|

Analysis Calculation

ax=g (sin θ−μ cos θ )

μk cosθ=sin θ− ag

μk=|sinθ−a

g|cosθ

¿|sin 30−125

9,8 |cos30

¿|12−125

9,8 |12√3

¿ 12,2512√3

=12,250,866

=14,15

∆ μk=|δ μk

δa∆ a|+|δ μk

δθ∆θ|

¿| −1gcosθ

∆ a|+|cos θ .cos θ−(sin θ−ag ) (−sin θ )

cos2 θ∆ θ|

¿| −1gcosθ

∆ a|+|cos2θ−(−sin2 θ+ag

sin θ)cos2θ

∆ θ|

¿| −1gcosθ

∆ a|+|cos2θ+sin2θ−ag

sin θ

cos2θ∆ θ|

∆ μk=| −1g cosθ

∆ a|+|1− ag

sinθ

cos2θ∆ θ|

∆ μk

μk

=| −1gcosθ

∆ a|+|1−ag

sin θ

cos2θ |sin θ−a

gcosθ

∆ μk={( −1

g(sin θ−ag )

∆ a)+( 1− ag sin θ

cosθ(sin θ−ag )

∆ θ)}μk

∆ μk=( ∆ a

g(sinθ−ag )

+( 1−ag

sin θ

cosθ (sin θ− ag )

∆ θ)) μk

¿( 0,25

9,8 (sin 30−1259,8 )

+( 1−1259,8

sin 30

cos30(sin 30−1259,8 )

1))14,15

¿( 0,25

9,8 ( 12−

1259,8 )

+( 1−1259,8

.12

12 √3( 1

2−125

9,8 )1))14,15

¿( 0,259,8 (12,25 )

+( 5,850,866 (12,25 ) ))14,15

¿ (0,002+0,55 )14,15

¿7,81

Relative Error

KR=∆ μk

μk

x100 %= 7,8114,15

x100 %=55,19 %

so , Physic Report=|μk ± ∆ μk|=|14,15 ± 7,81|

DISCUSSION

Based on the results of experiments that have been carried out as for the discussion of each activity that is the first to observe the activities of the state precise tensile force by observing the tensile force precise at montionless, object to uniform, and uniform line motion. At the time of montionless objects tensile force 1.5 N precise it shows that the friction force that occur in only a few precise so that the object remains montionless, when the object precise to uniform tensile force that arises in 1.8 N precise that prove force given on precise large enough to be able to uniform or experience static friction force and the last state of that is uniform motion line with a constant state of tensile force is 0,8 N precise so that the kinetic friction force caused by tensile force beams that arises from friction with the surface of the table.

In the second activity that looked at the relationship between the normal force with the frictional force on the state of montionless objects, precise to uniform and uniform motion line, but at montionless objects do not happen so that data can be compared when the object to uniform precise and uniform line motion. On the precise to uniform the object experiences a force of static friction with normal force different from the 1,90 N, 2.40 N and 3.40 N static friction force increases, 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. Further, when the state of the object uniform motion line experiencing 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.

Later in the third activity that looked at the relationship between the state of the surface of the friction force on the state of montionless objects, to uniform precise, and line beergerak irregular use two types of surfaces are a refined surface and rough surfaces. On a refined 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 activities that determine the coefficient of static friction on an inclined plane using a different gravity of the beam / load observed critical angle formed when the object has gravity 1,6 N, 2,1 N, and 2,6 N. In the first gravity is greater than the critical angle with gravity objects 2,3 and 4. From the experimental results it can be seen that the greater the gravity of a beam / object that formed the critical angle is getting smaller because of the attraction was the 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 activities of the five events, 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. Based on the experimental results showed that at 84 cm distance objects travel time to get to the end of the incline is less than the distance of 104,3 cm, and 124 cm. So, the closer the object of the incline the travel time it takes the less.

The factors that affect the friction force is the normal force object, gravity, tensile force, good thing it's kind of surface rough surface or smooth surface, but it also dipengaaruhi friction force by the state of things at the time the object was silent but silent when friction force objects are very small or none at all, at the time the object was precise to uniform objects having static friction force, and when the object was uniform line experiencing motion objects kinetic friction force.

Friction consists of two, namely static friction force and kinetic friction force. Static friction occurs when the object to uniform in the precise circumstances because the force that occurs at the same object with friction force. Kinetic friction occurs when a uniform object in a state of motion line because the force object that happens to be greater than the friction force experienced by objects / beam. In the known friction force coefficient of friction force. Coefficient of friction force consists of two, the coefficient of static friction and kinetic friction coefficient. As for how to determine the static friction coefficient can be determined by the formula (1) and to determine the coefficient of kinetic friction can be determined by the formula (2).

μs=f s

N……… ..(1)

μk=f k

N……….(2)

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. Frictional force at work when things move in the air , water , or glide over other solid objects.

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.

The factors that affect the friction force is the normal force object, gravity, tensile force, good thing it's kind of surface rough surface or smooth surface, but it also dipengaaruhi friction force by the state of things at the time the object was silent but silent when friction force objects are very small or none at all, at the time the object was precise to

uniform objects having static friction force, and when the object was uniform line experiencing motion objects kinetic friction force.

Friction consists of two, namely static friction force and kinetic friction force. Static friction occurs when the object to uniform in the precise circumstances because the force that occurs at the same object with friction force. Kinetic friction occurs when a uniform object in a state of motion line because the force object that happens to be greater than the friction force experienced by objects / beam. In the known friction force coefficient of friction force. Coefficient of friction force consists of two, the coefficient of static friction and kinetic friction coefficient. As for how to determine the static friction coefficient can be determined by the formula (1) and to determine the coefficient of kinetic friction can be determined by the formula (2).

μs=f s

N……… ..(1)

μk=f k

N……….(2)

And to find the acceleration of the frictional force we can use this formula:

ax = g (sin θ − μk cos θ )

REFERENCES

[1]Anomin. 2013. History. http://www.tribology-abc.com/abc/history.htm. Accessed at : Sunday, 10 November 2013, 11.00.

[2]Anonim. 2013. Friction. http://en.wikipedia.org/wiki/Friction. Accessed at : Monday, 11 November 2013, 16.34.

[3]Husna.2011.Laporan praktikum fisika. http://gusnablogspotcom.blogspot.com /2011/06/laporan-praktikum-fisika.html. Accessed at : Monday, 11 November 2013, 15.22.

[4]Septiawan. 2013. Laporan fisika. http://setiawanfiles.blogspot.com/2013/04/laporan-fisika.html. Accessed at : Monday, 11 November 2013, 15.01.