BLOG ENTRY: Pulley Lab Reflection
Blog Entry: Weight, Work Lab
What was our mission?
This lab allowed us to utilize the robots, along with varying masses and velocity measurements, to explore Newton’s 2nd law.
The law can be stated in formula form as F = ma.
Furthermore, the variables explored would heighten our understanding of the law of conservation of energy. This law states that energy is not created or destroyed, but is instead changed between different forms. To allow us to explore these rules, we measured velocity and acceleration using the computer program LabView. LabView also permitted the manipulation of power as a tool to further enhance our understanding of Newton’s 2nd law.
How did these experiments heighten our understanding?
Our lab focused on the conservation of energy through Newton’s 2nd law. To allow us to explore these laws, we did multiple test runs which manipulated one variable in each set of trials. By focusing on one variable at a time, we were able to highlight different relationships that would confirm the validity of these scientific rules.
Trial Set 1: Constant Mass
For our first four trials, we used the LabView program to alter the amount of power employed to carry the weights up the pulley. However, in these trials, we would maintain the same mass. By keeping mass the same, we are able to use the formula under Newton’s 2nd law to create a hypothesis on what the results will be. If mass is remaining the same, but force is going to increase, it is very likely that acceleration must also increase.
The following table shows the data recorded for the first set of trial runs:
| Speed (RPM) | Battery Discharge | Mass (kg) | Power | Time (sec) | Acceleration (RPM/sec.) |
|
30.850514 |
111 |
0.09 |
50 |
4.511 |
6.838952 |
|
66.496526 |
139 |
0.09 |
75 |
2.351 |
28.284358 |
|
106.949352 |
110 |
0.09 |
100 |
1.415 |
75.582581 |
|
106.567093 |
70 |
0.09 |
125 |
1.406 |
75.794519 |
Furthermore, a graph below underscores the relationship between acceleration and power:
As expected, as we increased the force imposed onto the pulley from the robot, the acceleration also increased. This matches with Newton’s 2nd law.
Trial Set 2: Constant Power
For our second set of trial runs, we did not adjust the power on LabView. Instead, we used the weights provided to us to alter the mass being carried up the pulley. This would allow us to focus on the other half of the Newton’s 2nd law. If mass were to increase, we would hypothesize that acceleration would have to decrease. This is given that the power is remaining the same. Without the drop in acceleration, the formula F = ma would not balance.
The following table shows the data recorded for the second set of trial runs:
| Speed (RPM) | Battery Discharge | Mass (kg) | Power | Time (sec) | Acceleration (RPM/sec.) |
|
23.724792 |
153 |
0.08 |
50 |
5.058 |
4.690548 |
|
24.856242 |
139 |
0.1 |
50 |
5.391 |
4.610692 |
|
15.795495 |
139 |
0.12 |
50 |
7.576 |
2.084939 |
|
2.115704 |
194 |
0.16 |
50 |
9.847 |
0.214858 |
Furthermore, a graph below underscores the relationship between mass and acceleration:
Fitting with the formula/law, the acceleration decreased as mass increase. The two variables have an inverse relationship. This data means that the two will still equate to the power (force) that we input onto LabView, re-enforcing Newton’s 2nd law.
How did this enhance understanding of the law of conservation of energy?
For the last portion of our lab, we measured the height of the pulley and analyzed the battery discharge information from LabView. What this allowed us to do what look at the relationship between the amount of battery utilized and the potential energy, which can be measured with the following formula:
PE = mgh
We divided this by the time on LabView, using Microsoft Excel, to get the needed data for our graph below. The information is also shown in table form:
| Gravity(m/s2) | Mass(kg) | Height (km) | Time (sec) | PE | PE/T | Battery Dischage |
|
9.8 |
0.08 |
0.04 |
5.058 |
0.158619 |
0.03136 |
153 |
|
9.8 |
0.1 |
0.04 |
5.391 |
0.211327 |
0.0392 |
139 |
|
9.8 |
0.12 |
0.04 |
7.576 |
0.356375 |
0.04704 |
139 |
|
9.8 |
0.16 |
0.04 |
9.847 |
0.617604 |
0.06272 |
194 |
|
9.8 |
0.09 |
0.04 |
4.511 |
0.159148 |
0.03528 |
111 |
|
9.8 |
0.09 |
0.04 |
2.351 |
0.082943 |
0.03528 |
139 |
|
9.8 |
0.09 |
0.04 |
1.415 |
0.049921 |
0.03528 |
110 |
|
9.8 |
0.09 |
0.04 |
1.406 |
0.049604 |
0.03528 |
70 |
We noticed that our graph, disregarding the two outside data points in the top right and lower center, was generally stable. While we would have expected more of an increase in battery discharge given a higher PE/T value, we attribute it to the fact this lab did not require heavy battery usage. However, we were able to conclude that this is an area we would see the conservation of energy between the potential energy and energy used on the pulley.
Conclusion
This lab was a fun, interactive way to enhance our understanding of Newtons’ 2nd law and the law of conservation of energy. Furthermore, my relationship with Rebecca continued to strengthen as we went through each trial. We communicate clearly and divide up the tasks without any issue! I can’t wait to continue enhancing my understanding of the class material in the lab!
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