Ah 05 b coefficient of friction(wood and felt on plastic track)

AH-05B: Coefficient of Friction (Wood and Felt on Plastic
Track)
Rev: 1-10-2021
OBJECTIVE
The purpose of this experiment is to calculate the coefficients
of kinetic and static friction between the track and two different
surfaces (wood and felt), for two different surface areas as they
slide relative to each other. We use the track in a horizontal
position and then as an inclined plane.
VIDEO: You can see the experimental process in this video in
which this experiment is done on a Formica table instead of the
track. This is only to give you an idea on how to do the
experiment. Do NOT take the data from the video.
https://youtu.be/BAl3o6-9RF0
MATERIALS
1. ME-6960 PASTrack 4. ME-9807 Friction Block
2. ME-9448B Pulley 5. ME-8979 Weight hanger and
weights
3. ME-9495A Angle Indicator 6. Black String
1- ME-6960: PASTrack Unassembled PASTrack Assembled

2- ME-9448 Super Pullley 3- ME-9495 Angle Indicator
4- ME-9807 Friction Block 5- ME-8979 Weight hanger and
weights
INTRODUCTION
In general, friction is the force that slows down the motion of
an object. The force of friction is directed along the surface of
contact between the object and surface and directed opposite to
the direction of motion of object (or the direction of impending
motion). We deal with:
a) Static friction ( fs)
This exists when the object is at rest relative to the surface.
This force must be overcome in order to make the object start
moving. Its value increases to match the external force trying to
cause the object to move. It is given by: fs ≤ µs n, where n is
the normal force, and µs is the coefficient of static friction. The
maximum value of static friction is fs = µs n.

b) Kinetic friction ( fk)
This exists when the object is in motion and is given by fk =
µkn, where µk is the coefficient of kinetic friction and n is the
normal force which presses the two surfaces together. In
general, µs > µk because it takes a larger force to start an object
sliding (static friction) than to keep it sliding (kinetic friction).
Both coefficients depend only on the materials in contact and
are independent of the area of contact, or the normal force.
In this experiment, using the track in a horizontal position, we
measure the frictional force fk and fs for different values of the
normal force n. By using these, we calculate the two
coefficients of friction between block and board.
Another way to find µs is to set up the board as an inclined
plane. The coefficient of friction µs is related to the maximum
angle θm to which the board can be elevated before the block
starts to slip by the equation:
θm
θm
µs = tan θm ( 1 )
EXPERIMENTAL PROCEDURE
Kinetic Friction
1) Assemble the Track. To do this, read the manual that came
with the track, and see the video: Assembling the Track. At the
end, you may dis-assemble it, for which you can see the video:
Dis-assemble the track. Both videos are in the module: LAB
VIDEOS.
2) Take the mass of the Friction block as 110 grams.
3) Attach a pulley at the end of the track. Tie a string to the

Friction Block and pass it over the pulley. Attach weight hanger
to the string by wrapping the thread in the notch in the plastic
hanger.
4) First, keep the large wooden side of the friction block on the
track.
5) Slowly increase the weights on the weight hanger, until the
block starts slowly moving with constant speed aftergiven a
small push. Don’t forget to include the mass of the hanger. Use
your judgement to see if the speed is constant.
6) Repeat the above procedure by adding 100, 200 and 300
grams on the friction block.
7) Repeat steps 5 and 6 with felt side of the friction block at the
bottom.
8) Repeat steps 5 and 7 with the small sides of the friction
Block. This time, use only 200 grams on the Friction Block. Do
a total of 3 independent trials and record your data.
Use the data to plot a graph between friction force on the Y-axis
(equal to the hanging mass in kilograms times g) and normal
force on the X-axis (equal to the mass of friction block plus any
masses on it times g), and hence find the coefficient of kinetic
friction.
Static Friction
9) Set up the friction block again with the wide wood side on
the track, and place a mass of 200 g on it. Place weights gently
on the hanger and increase them slowly until the block just
starts its motion without any push. Do a total of 3 independent
trials and record your data.
10) Repeat step 9 with the felt side ion the track.
Use the data to calculate the coefficient of static friction.
11) Remove the pulley and use the track as an inclined plane.
Attach the angle indicator to the track. Place 200 g on the

friction block, and use tape to hold them there. With the Large
wood side on the track, gently and smoothly tip the track until
block starts to move (once it starts to move, static friction
changes to kinetic friction, and the block accelerates down the
track). Measure the angle θm at which the block just starts to
slip, and record it in the table. Do a total of 3 independent
trials. Use angle θm to calculate the coefficient of static
friction.
12) Repeat step 11 with the large felt side at the bottom.
CALCULATIONS
1) For kinetic friction, plot the points and draw the best fit
graph of the friction force ( fk ) on the Y-axis versus the normal
force ( n ) on the X-axis, and find the coefficient of kinetic
friction between block and board from the slope of the curve.
(For how to make Best Fit Graph, see Lab-1: Error and Data
Analysis)
2) For static friction, use fs = µs n to calculate µs .
3) The percent difference is given by:
Percent difference = [difference of the two values /
average value] x 100 %
RESULTS:
Make a table of results showing the measured values of friction
coefficients, their errors, and values that you find on the
internet for these surfaces.
ADDITIONAL INFORMATION
Video of this experiment done on a table instead of the track:
https://youtu.be/BAl3o6-9RF0
Coefficient of Static Friction:
Manual device:
https://www.youtube.com/watch?v=xOXI7UBkZNM
Automatic device:
https://www.youtube.com/watch?v=yVdiWN6rHjs

Notice how the force changes as soon as the object starts to
move (static friction changes to kinetic friction):
https://www.youtube.com/watch?v=F8n3mVdMtDI
AH-05B - Coefficient of Friction REPORT
FORM
Name: _______________________________
LARGE WOOD SIDE ON TRACK
Mass of Friction Block (Mb): _________ Mass of
hanger (Mh): ________________
Normal and Friction force for kinetic friction
Mass on Friction Block
( M )
Normal Force ‘n’ (newtons)
(Mb + M)*g
Suspended mass + mass of hanger (grams)
Ms + Mh
Friction Force ‘fk’ (newtons)
(Ms + Mh)*g
0 kg

0.100 kg
0.200 kg
0.300 kg
µk from graph of friction force Vs normal force (i.e. fk Vs n):
________
Normal and Friction force for static friction
Mass on friction block (grams)
(M) grams
(Mb + M)*g
Ms + Mh
(Ms + Mh)*g
µs
200
200

200
Average
Inclined plane for static friction
Trial No.
Angle θm
µs
1
2
3
Average
Percent difference between the two values for µs :
_____________
Average of the two values of µs : _____________
LARGE FELT SIDE ON TRACK

hanger (Mh): ________________
Mass on Friction Block
( M )
(Mb + M)*g
Ms + Mh
(Ms + Mh)*g
0 kg
0.100 kg
0.200 kg
0.300 kg
µk from graph (of fk Vs n) ________
Normal and Friction force for static friction
Mass on friction block (grams)
(M) grams
(Mb + M)*g

Ms + Mh
(Ms + Mh)*g
µs
200
200
200
Average
Inclined plane for static friction
Trial No.
Angle θm
µs
1
2
3

Average
Percent difference between the two values for µs:
_____________
Average of the two values of µs: _____________
SMALL WOOD SIDE ON TRACK
hanger (Mh): ________________
Mass on friction block
( M ) kg
(Mb + M)*g
Ms + Mh
(Ms + Mh)*g
µk
0.200
0.200

0.200
Average µk
SMALL FELT SIDE ON TRACK
Mass of Friction Tray (Mb): _________ Mass of hanger
(Mh): ________________
Mass on friction block
( M ) kg
(Mb + M)*g
Ms + Mh
(Ms + Mh)*g
µk
0.200
0.200

0.200
Average µk
RESULTS
Coefficient of Kinetic Friction
Coefficient of Static Friction
Large Wood Surface
Large Felt Surface
Small Wood Surface
Small Felt Surface
Large Wood Surface
Large Felt Surface
Experimental values
Values found from internet

Percent error
OL-03 Addition of Vectors
Rev: 8/24/2019
OBJECTIVES
When a number of forces passing through the same point, act on
an object, they may be replaced by a single force which is
called the resultant or the sum. The resultant therefore is a
single force which is similar in effect to the effect produced by
the several forces acting on the body. It is therefore a single
force that replaces those forces. The objectives of this lab are to
use graphical and analytic methods to:
1. Resolve a force vector into its rectangular components, and
2. To find the resultant of a number of forces acting on a body.
This Manual was made for in-class lab. Since this lab is to be
done at home, only the Graphical and Analytical parts are to be

done. Do these on paper, take nice pictures, and upload with
your report.
APPARATUS
· A protractor
· Sheets of plain or graph paper.
· Ruler
· Pencil
THEORY OF VECTOR ADDITIONa. Graphical
MethodsParallelogram Method
R
B
A
Vectors are represented graphically by arrows. The lengt h of a
vector arrow (drawn to scale on graph paper) is proportional to
the magnitude of the vector, and the arrow points in the
direction of the vector. The length scale is arbitrary and usually
selected for convenience so that the vector graph fits nicely on
the graph paper. See Fig 1a, where R = A + B. The magnitude R
of the resultant vector is proportional to the length of the
diagonal arrow and the direction of the resultant vector is that
of the diagonal arrow R. The direction of R may be specified as
being at an angle θ relative to A.
Figure 1a
B
A
R
Triangle Method
An equivalent method of finding R is to place the vectors to be
added "head to tail" (head of A to tail of B, Fig. l b). Vector

arrows may be moved as long as they remain pointed in the
same direction. The length and direction of the resultant is
measured from the graph.
Figure 1b
Polygon Method
If more than two vectors are added, the head-to-tail method
forms a polygon (Fig. 2). For four vectors, the resultant R = A +
B + C + D is the vector arrow from the tail of the A arrow to the
head of the vector D. The length (magnitude) and the angle of
orientation of R can be measured from the diagram.
Figure 2
b. Analytical MethodsTriangle Method
B
A
C
α
γ
β
The magnitude of R in Fig. 3 can also be computed by using
trigonometry.
The Law of Sines and the Law of Cosines are especially useful
for this:
Law of Sines: A/Sin α = B / Sin β = C / Sin γ. (3-1)
Law of Cosines: C2 = A2 + B2 – 2AB Cos γ (3-2)

Figure 3
Method Of Components
A vector A can be writtenas a sum of two vectors Ax and Ay
along the x and y axis respectively, as shown. We call them the
components of vector A and are given by:
Ax = Acosθ i (3-3)
Ay = Asinθ j (3-4)
where θ is the angle between the vector A and the x axis.
In order to find the resultant vector R of a system of vectors A,
B, C, etc…
we follow these steps:
a) Find the x and y components for each vector using the above
equations.
i.e. find Ax, Bx, Cx ... and Ay, By, Cy ....
Remember they can be positive or negative depending on
their direction.
b) Add up these components to get:
Rx = Ax + Bx + Cx + … (3-5)
Ry = Ay + By + Cy + … (3-6)
c) Now, the magnitude of R is : [Rx2 + Ry2] ½
The direction of R is : θ = tan -1 [Ry / Rx] where θ is
the angle between R and x axis.
If θ > 0 then R is either in the 1st or 3rd quadrant
If θ < 0 then R is either in the 2nd or 4th quadrant.
PROCEDURE
It would be good if you can print pages 4 to 7, and draw the
vectors on them. If that is not possible, draw the vectors on
white sheets of paper using the scale mentioned here.
1) VECTOR RESOLUTION: Consider a force vector = 300 N at
the 40º angle. Resolve this vector into its x- and y-components
by the following methods:
A) Graphical: Make the X- and Y-axes. Use a scale of 30 N =

1.0 cm, and draw an arrow of appropriate length at 40º. Drop
perpendiculars from the tip of the vector to the X- and Y-axes.
Measure the lengths of these lines and hence find the
magnitudes of Fx and Fy. (do not calculate using trigonometry)
Record the results.
B) Analytical: Compute the magnitudes of Fx and Fy by
using the Component Method (equations 3-3 and 3-4). Record
the results.
2) VECTOR ADDITION: Find the sum of two ‘forces’: 100 N at
30º and 200 N at 120º, by:
A) Graphical Method: Make the X- and Y-axes. Use a scale of
25 N = 1.0 cm. Draw arrows of appropriate lengths at 30º and
120º, both starting from the origin. Add them using the
Parallelogram method. Measure the length and angle of the
resultant. Convert length to magnitude of the resultant vector
using the scale used to draw the vectors. Record the results in
the Data Table.
B) Analytical Method: Compute the sum of the two vectors
by using the Component Method (equations 3-3 and 3-4) as well
as the Triangle Method (equations 3-1 and 3-2). Record the
results in the Data Table.
3) VECTOR ADDITION: In addition to the two forces of
procedure 2, add a third force = 150 N at 230º. Find the vector
sum by A) Graphical and B) Component methods, and record in
the Data Table. Use a scale of 25 N = 1.0 cm for the graphical
method.
CALCULATIONS
Show your calculations for the analytic method and the method
of components.

RESULTS
Write the results in the Table of Results on page 7.
ADDITIONAL INFORMATION:
http://www.physicsclassroom.com/class/vectors/u3l1b.cfm
http://phet.colorado.edu/sims/vector-addition/vector-
addition_en.html
https://www.youtube.com/watch?v=ZYbX8cL5LNE
OL-03 Addition of Vectors
REPORT FORM
Name: ___________________________________
Date: _______________
1-A: VECTOR RESOLUTION: Resolve the Force vector F =
300 N at the 40º angle into its X- and Y-components, by using
the Graphical Method. Use Scale: 30 N = 1.0 cm.
Result:
Fx = ______ cm = ______ N
Fy = ______ cm = ______ N
1-B: VECTOR RESOLUTION: Resolve the Force vector F =
300 N at 40º angle into its X- and Y-components, by using the
Component Method.

2-A: VECTOR ADDITION: Find the sum of two forces: R = A
+ B, where A=100 N at 30º and B=200 N at 120º, by using
Graphical Method: Scale: 25 N = 1.0 cm.
Use Parallelogram method.
N
Results:
Magnitude = ___
Direction = _____

2-B: VECTOR ADDITION: Find the sum of two forces: R = A +
B, where A=100 N at 30º and B=200 N at 120º, by using the
Component Method, and Triangle method (egn. 3-1 and 3-2).
3-A: VECTOR ADDITION: Find the sum of three forces R = A
+ B + C, where A=100 N at 30º, B=200 N at 120º, and C=150 N
at 230º by Graphical Method: Use a scale of 25 N = 1.0 cm.
Use Polygon Method (Tip-To-Tail rule).
N
Result:
Magnitude = ___
Direction = _____

3-B: VECTOR ADDITION: Find the sum of three forces R = A
+ B + C, where A=100 N at 30º, B=200 N at 120º, and C=150 N
at 230º by the Component Method.
RESULTS
FORCE/S
R E S U L T S
GRAPHICAL METHOD
ANALYTICAL
(TRIANGLE METHOD)
ANALYTICAL (COMPONENT METHOD)
VECTOR RESOLUTION
F= 300 N,
θ = 40º
Fx =
Fy =

Fx =
Fy =
VECTOR ADDITION
(TWO FORCES)
F1 = 100 N,
θ = 30º
F2 = 200 N,
θ = 120º
Mag =
Dir =
Mag =
Dir =
Mag =
Dir =
VECTOR ADDITION
(THREE FORCES)
F1 = 100 N,
θ = 30º

F2 = 200 N,
θ = 120º
F3 = 150 N,
θ = 230º
Mag =
Dir =
Mag =
Dir =
4

Ah 05 b coefficient of friction(wood and felt on plastic track)

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to Ah 05 b coefficient of friction(wood and felt on plastic track)

Similar to Ah 05 b coefficient of friction(wood and felt on plastic track) (20)

More from AASTHA76

More from AASTHA76 (20)

Recently uploaded

Recently uploaded (20)

Ah 05 b coefficient of friction(wood and felt on plastic track)