On 31 January 2012 we conducted an experiment in class to help us better understand the concept of energy. Though definitions there are in superabundance, it is as difficult for me to fully grasp the concept of energy as it is for most people to fully grasp the concept of love. I just know that love is and know what the experience feels like. Likewise, I know that energy exists and associate it with my experiences therewith, e.g., movement.
As with most technical terms, one is led on an interminable journey through the dictionary in order to get a solid understanding of the word. Energy was defined in class as the ability to do work, which is in turn defined as the process by which energy is transferred from one object to another. Each definition contains the term which is sought to be defined – a seeming conundrum, that.
Enter the discipline of science, where empirical experimentation is the order of the day. And our class project sought to further demystify this ubiquitous term, energy, by conducting an exercise to gauge how energy is utiliized to raise a certain mass to a certain height.
Our device was a pulley with a cylindrical mass attached to it. The pulley was rigged to lift the mass via a computer software program. We did a total of 8 runs, alternating the mass with the power level remaining constant at 50% on four of the runs, and alternating the power levels with the mass remaining constant at 0.25 kg on the other four runs.
| Speed (RPM) | Battery Discharge (mv) |
Mass (kg) | Power Level (%) | Time (s) | Acceleration | Height (m) | g (m/s^2) | MGH | |||||||
| Constant Power Level | |||||||||||||||
| 0 | 0.08871 | 0 | 138 | 0 | 0.24 | 0 | 50 | 0 | 1702.17 | 0 | 5.21E-05 | 0.2 | 9.8 | 0.4704 | |
| 0 | 0.076954 | 0 | 138 | 0 | 0.23 | 0 | 50 | 0 | 1734.802 | 0 | 4.44E-05 | 0.2 | 9.8 | 0.4508 | |
| 0 | 0.087218 | 0 | 83 | 0 | 0.13 | 0 | 50 | 0 | 1784.809 | 0 | 4.89E-05 | 0.2 | 9.8 | 0.2548 | |
| 0 | 0.068573 | 0 | 41 | 0 | 0.25 | 0 | 50 | 0 | 2447.497 | 0 | 2.80E-05 | 0.2 | 9.8 | 0.49 | |
| Constant Mass | |||||||||||||||
| 0 | 0.072024 | 0 | 70 | 0 | 0.25 | 0 | 60 | 0 | 1872.049 | 0 | 3.85E-05 | 0.2 | 9.8 | 0.49 | |
| 0 | 0.081327 | 0 | 138 | 0 | 0.25 | 0 | 80 | 0 | 1932.529 | 0 | 4.21E-05 | 0.2 | 9.8 | 0.49 | |
| 0 | 0.07907 | 0 | 27 | 0 | 0.25 | 0 | 100 | 0 | 1996.121 | 0 | 3.96E-05 | 0.2 | 9.8 | 0.49 | |
| 0 | 0.08298 | 0 | 27 | 0 | 0.25 | 0 | 105 | 0 | 2034.625 | 0 | 4.08E-05 | 0.2 | 9.8 | 0.49 | |
As can be seen from the above data, when the mass is constant and the power levels are different, potential energy (mgh) is constant. But, when the mass changes while the power levels remain constant, we see that potential energy (mgh) changes. Potential energy was defined in class as energy that a body has that is not being spent.