Name: Qiwen Ye (Sherry)
Lab partners names: Jae Yoo, Chandler
Date: 21-Sep-2016
2. 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
-- Introduction:
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:
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. First, weigh a wooden block that has felt on one face of it. Placed the felt-side of the block on the lab table. Tie a string to the block and over a pulley at the end of the lab table. Second, opened up a paper clip and bend the ends so that they form a handle on a Styrofoam cup (just line the handle on a pail.) Connected the string to the middle of the handle. Third, Patently the mass to the bottom of the string at a time, until the block finally starts to slide. Record the mass to get the block to start to move. Then, added the mass on the block in order to change the mass of the block, repeated process again to get what mass can start to move the new mass of the block.
-- A table of the Data:
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:
-- A table of calculated results/Graphs of data:
Draw the free body diagram we got:
Then, we calculated the values of friction force and normal force by those equation:
Finally, we got the table about the mass of hanging, the mass of the block, the static friction and the normal force of the mass of the block:
By using the LabPro, we got the graph about the friction force vs. normal force.
We calculated our theoretical values of the coefficient of static friction by get the average of four values of friction force and normal force:
That, we got our theoretical values of the coefficient of static friction is 0.26713395638
-- Explanation of graph/analysis
There is the graph 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 0.2662, there is our experimental value the coefficient of static friction.
-- Conclusion:
In this experiment, we determined the coefficient of static friction between the felt and the track . The experimental value is 0.2662, and the theoretical values is 0.26713395638. The error percent is 0.34%. This result shows that the experimental value is very close to the theoretical value. Therefore, this experiment is successful.
-- Introduction:
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. Kinetic friction is independent of the the area or speed of the moving object, it is being proportional to the normal force. That is, we wrote
In this Kinetic friction experiment, we used a Force sensor. First, we had to calibrate the 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.
-- A table of calculated results/Graphs of data:
By the free body diagram we got
Then, we 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.
By using the LabPro, we got the graph about the kinetic friction force vs. normal force.
We 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 0.21309370988
-- Explanation of graph/analysis:
The slope of the graph the kinetic friction force vs. normal force is experimental value of the coefficient of kinetic friction between the block an the table, there is 0.2118.
-- Conclusion:
In this experiment, we determined the coefficient of kinetic friction between the block and the table. The experimental value is 0.2118, and the theoretical values is 0.21309370988. The error percent is 0.61%. This result shows that the experimental value is very close to the theoretical value. Therefore, this experiment is successful.
-- Apparatus/ Experiment 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 28 degree.
-- A table of calculated results/Graphs of data:
We calculated the coefficient of the kinetic friction of the sloped surface.
-- Explanation of graph/analysis:
By the equation, we determined the coefficient of static friction between the block and the surface is 0.5095.
-- Conclusion:
In this experiment, we found the relationship between the angle of the surface and the static friction is that the static friction is depended on the angle.
(4) Kinetic Friction From Sliding A Block Down An Incline
-- Apparatus/ Experiment 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:
Used the iPhone - compact to measure an angle, the angle is 27 degree. Through the LabPro, we got the acceleration is this motion. In the graph of velocity vs. time, the acceleration is its slope, a=2.585 m/s^2.
-- A table of calculated results/Graphs of data:
We calculated the coefficient of the kinetic friction of the sloped surface.
-- Explanation of graph/analysis:
The slope of the graph is the acceleration of the block, so that while we 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 0.21.
-- Conclusion:
In a incline, the kinetic friction depends on the acceleration of the object and the angle of the incline.
(5) Predicting the Acceleration of A Two-Mass System
-- Apparatus/ Experiment 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.
The mass of block is 0.18 kg, the mass of hanging is 0.08 kg, and we used the kinetic friction results from experiment (4) above.
We got the graph velocity vs. time by the LabPro.
-- A table of calculated results/Graphs of data:
We calculated the Theoretical acceleration in this way.
The experimental acceleration is the slope of the graph velocity vs. time. The experimental value of acceleration is 1.556 m/s^2. The theoretical acceleration is 1.591 m/s^2.
-- Conclusion:
In this experiment, we predicted the acceleration of a two-mass system. The experimental value of the acceleration is 1.556 m/s^2, and the theoretical values is 1.591 m/s^2. The error percent is 2.2%. This result shows that the experimental value is close to the theoretical value. Therefore, this experiment is successful.
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