hopefully, this report can help you a lot ^^

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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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.