Ian Lin, Kirk Paderes, Jorge Avalos
3/22/17
Determine the coefficient of static and kinetic friction in horizontal and inclined surfaces.
Frictional force can be divided into two categories: static and kinetic friction. Static friction describes the friction force acting between two bodies when they are not moving relative to one another. Kinetic friction describes the friction force acting between two bodies when they are moving past one another. Both types of friction are characterized by a coefficient of static /kinetic friction. In the scenarios that follow, a graph of the force of friction vs the normal force is plotted, and the slope of that graph is the coefficient of friction.
Setup the experiment for case 1 by hanging mass from the pulley connected to the block by a string. Continue to attach mass until the block just starts to move.
In case 2, a force sensor and a computer is necessary to detect the motion of the block. Start by calibrating the force sensor and setting up the lab equipment. Pull the block with a constant speed by attaching a string from the block to the force sensor.
In case 3, the coefficient of static friction is measured by raising the surface at an angle relative to the horizontal and measuring the angle at which the block starts to slip.
In case 4, with a motion detector in place, raise the incline to an angle until the block accelerates and measure the coefficient of kinetic friction between the block and the surface.
Experiment 1
|
Mass of block 1
|
173±
1
|
Grams
|
Hanging mass 1
|
65 ±
1
|
Grams
|
Mass of block 2
|
373 ±
1
|
grams
|
Hanging mass 2
|
165 ±
1
|
Grams
|
Mass of block 3
|
573 ±
1
|
Grams
|
Hanging mass 3
|
260 ±
1
|
Grams
|
Mass of block 4
|
773 ±
1
|
Grams
|
Hanging mass 4
|
355 ±
1
|
Grams
|
Experiment 2
Tension 1
|
0.44
|
Newton
|
Mass of block 1
|
173 ± 1
|
Grams
|
Tension 2
|
1.54
|
Newton
|
Mass of block 2
|
373±
1
|
Grams
|
Tension 3
|
1.54
|
Newton
|
Mass of block 3
|
573 ±
1
|
Grams
|
Tension 4
|
2.19
|
Newton
|
Mass of block 4
|
773 ±
1
|
Grams
|
Experiment 3
|
Ø
|
30.2 ± 0.1
|
North of west
|
Mass of block
|
173 ± 1
|
Grams
|
Experiment 4 |
Ø
|
30.2 ± 0.1
|
North of west
|
Mass of block
|
197 ± 1
|
Grams
|
Acceleration
|
2.219
|
m/s/s
|
Experiment 5
|
Hanging mass
|
206 ± 1
|
Grams
|
Mass of block
|
173 ± 1
|
Grams
|
Acceleration
|
4.37
|
m/s/s
|
Experiment 1
|
Coefficient of static friction
|
Mass of block 1
|
0.002592 ± 0.00286
|
Mass of block 2
|
0.002753 ± 0.00286
|
Mass of block 3
|
0.0026876 ± 0.00286
|
Mass of block 4
|
0.0028331 ±0.00286
|
Experiment 2
|
Coefficient of static friction
|
Mass 1
|
0.002592 ±0.00286
|
Mass 2
|
0.002753 ± 0.00286
|
Mass 3
|
0.0026876 ± 0.00286
|
Mass 4
|
0.0028331 ± 0.00286
|
Experiment 3
|
Coefficient of static friction
|
µ
|
0.582 ± 0.002
|
Experiment 4
|
Coefficient of kinetic friction
|
µ
|
0.320 ± 0.028
|
Experiment 5
|
Numerical value
|
Units
|
Calculated acceleration
|
3.89505 ± 0.3714
|
m/s/s
|
Measured acceleration
|
4.37 ± 0.2375
|
m/s/s
|
The graphs above are generated by the motion sensor and the force sensor for the experiments in cases 1, 2, and 4. They show the position, velocity, and force vs time for the cases mentioned, and these were useful because of the relationship between position and velocity. In addition, the critical force exerted was necessary in order to derive the values of the coefficient of kinetic and static friction. The coefficient of friction is the slope of the exerted force vs the normal force.
In conclusion, this lab was surprisingly frustrating because of the disparities in number of blocks in order to get the block moving in the first case. All the other cases were relatively simple with case 2 as just exerting a constant force so that the block moved horizontally at a constant speed. Case 3 was just a case of measuring the angle of incline, and case 4 was just deriving an equation for the coefficient of kinetic friction between the block and the surface and plugging in the measured values for acceleration and angle of incline. The major source of error in this lab is human consistency and negligence in pulling and adding blocks, and the uncertainty in the original measurements for the masses of the blocks and angles of incline could propagate in the values for the acceleration of the block and the coefficient of kinetic friction between the block and the surface. Lastly, for case 5 on predicting the acceleration of a two-mass system, the calculated acceleration value was 6.76 ± 0.12 m/s/s compared to the value of the measured acceleration 4.37 ± 0.2375 m/s/s. That's a 50% difference. Clearly, the experimental results strongly disagrees with the theoretical results.
In conclusion, this lab was surprisingly frustrating because of the disparities in number of blocks in order to get the block moving in the first case. All the other cases were relatively simple with case 2 as just exerting a constant force so that the block moved horizontally at a constant speed. Case 3 was just a case of measuring the angle of incline, and case 4 was just deriving an equation for the coefficient of kinetic friction between the block and the surface and plugging in the measured values for acceleration and angle of incline. The major source of error in this lab is human consistency and negligence in pulling and adding blocks, and the uncertainty in the original measurements for the masses of the blocks and angles of incline could propagate in the values for the acceleration of the block and the coefficient of kinetic friction between the block and the surface. Lastly, for case 5 on predicting the acceleration of a two-mass system, the calculated acceleration value was 6.76 ± 0.12 m/s/s compared to the value of the measured acceleration 4.37 ± 0.2375 m/s/s. That's a 50% difference. Clearly, the experimental results strongly disagrees with the theoretical results.
No comments:
Post a Comment
Note: Only a member of this blog may post a comment.