Purpose: The purpose of this lab is create a
model to determine the behavior of an object when friction is involved.
Purpose
In this lab, we did five different experiments
involving friction: static friction, kinetic friction, static friction friction
from a sloped surface, kinetic friction from sliding block down an incline and
predicting the acceleration of a two-mass system. We used the derivation and
measurement and capture the appropriate graphs to explain how we can get the
friction from each section of the lab in order to find each friction of
experimental values compared to the theoretical values.
(1) Static Friction
Static friction describes the friction force
acting between two bodies when are not moving relative to one another. The
coefficient of static friction is defined as:
procedure:
In this static friction experiment, we added the
mass m to the bottom shown a bit of time until the block just starts to slip.
We run the experiment and record the appropriate
data by repeating the experiment in four times, so that we got four different
values of mass of hanging and mass of block that the block start to move:
Mass (block)
|
Mass (hanging)
|
182g
|
105g
|
382g
|
205g
|
582g
|
380g
|
782g
|
500g
|
-- A table
of calculated results/Graphs of data:
Calculated
the values of friction force and normal force by those equation:
We
calculated our theoretical values of the coefficient of static friction
That, we got
our theoretical values of the coefficient of static friction is 0.288
Conclusion
The graph is
about the friction force vs. normal force, and the slope of the graph is the
values of the coefficient of static friction between the felt and the track. The
slope of the graph is 0.288, there is our experimental value the coefficient of
static friction.
(2) Kinetic
Friction
In our
model, the kinetic friction force has a fixed value for a given N, regardless
of the speed of the motion. This coefficient, like the coefficient of static
friction, depends only on the surface materials, not on the weight of the
object or its area of contact.
procedure:
In this Kinetic friction experiment, we used a
Force sensor. Opened in a LabPro and connected it to the computer with the USB
cable. Plug the force probe into the LabPro, CH1. Switch the force probe so
that it reads in the 10-N range. Second, connected up a force sensor to CH1 of
a LabPro and plug the LabPro into the computer, etc. Set the force sensor on
the 10-N range. Calibrate the force sensor using a 500-gram hanging mass. Then,
determined the mass of a wooden block that has felt on its lower surface.
Hold the force horizontally and Zero the force sensor. Finally, tie a string
between the force and sensor and the block to hit "collect" and
slowly pull horizontally, moving the block at constant speed along the surface
of the table. Store the run, and repeated the above step again to four
different mass of the block.
-- A table of the Data:
We run the
experiment and record the appropriate data by repeating the experiment in five
times, so that we got five different values of the mass of the block and the
value of the force senor.
Force (N)
|
F (mean)
|
182g
|
0.5077
|
382g
|
1.093
|
582g
|
1.652
|
782g
|
2.23
|
982g
|
2.743
|
calculated
results
Calculated
the normal force by
We got the
new table about the values of the mass of the block, the value of the force
senor, and the normal force.
mass
|
Force
|
N
|
182g
|
0.5077
|
1.7836
|
382g
|
1.093
|
3.7436
|
582g
|
1.652
|
5.7036
|
782g
|
2.23
|
7.6636
|
982g
|
2.743
|
9.6236
|
Get the
graph about the kinetic friction force vs. normal force.
Calculated
our theoretical values of the coefficient of kinetic friction by get the
average of four values of friction force and normal force:
That, we got
our theoretical values of the coefficient of kinetic friction is 0.288
(3) Static Friction
from A Sloped Surface
procedure:
Placed a block on a horizontal surface. Slowly
raised one end of the surface, and tilting it until the block starts to slip.
Used the angle at which slipping just begins to determine the coefficient of
static friction between the block and the surface.
-- A table
of the Data:
Used the
iPhone - compact to measure an angle the the block just begins to slip down,
the angel is 26.8, 30.2 and 32.6 degree.
Conclusion:
By the
equation, we determined the coefficient of static friction between the block
and the surface is 0.322.
(4) Kinetic
Friction From Sliding A Block Down An Incline
procedure:
Used a
motion detector to record the acceleration which at the top of an incline steep
enough that a block will accelerate down the incline. Measured the angle of the
incline and the acceleration of the block.
-- A table
of the Data:
The angle is
22 degree. Through the LabPro, we got the acceleration is this motion. In the
graph of velocity vs. time, the acceleration is its slope, a=0.7433 m/s^2.
Results:
--
Explanation of graph/analysis:
Plug the
number of the acceleration into the equation of the kinetic friction, we can
get the value of the coefficient of the kinetic friction in the sloped surface.
The coefficient of the kinetic friction is 0.322.
(5)
Predicting the Acceleration of A Two-Mass System
Procedure:
Set up the
motion sensor at end of the table, and placed the block in front of the motion
sensor. Used the string to connect the block and the hanging mass. Added the
mass of hanging in order to create the kinetic friction that the block was
moving forward.
Conculsion:
The experimental acceleration is the slope of
the graph velocity vs. time. The experimental value of acceleration is 3.771
m/s^2. The theoretical acceleration is 3.63 m/s^2.
x
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