Lego Mindstorm Pulley Lab
For this lab, I set out to explore Newton’s 2nd law of motion (Force = Mass * Acceleration ) and the Law of Conservation of Energy ( Energy = Mass * Acceleration * Height ). Using a Lego Mindstorm Robot, a set of pulleys and weights, I was able to test and observe these various laws in action.
Part 1.
For the first experiment, I set up the pulley apparatus and connected it to the Mindstorm drive motor which I set to apply a constant power regardless of the load (power level 50 in this case ).
| Mass (kg) | Acceleration (m/s^2) | Power |
| 0.2 | 17.012821 | 50 |
| 0.16 | 22.135246 | 50 |
| 0.14 | 27.969872 | 50 |
| 0.12 | 42.530809 | 50 |
By the data above, it’s clear that as the mass decreases, the acceleration of the object increases as it’s masses increases; according to Newton’s 2nd Law that is what I should expect. All to the good.
Part 2.
For the second part, we tested the relationship between power and acceleration. To do this, I kept the mass constant and changed the power level of the Mindstorm.
| Power | Acceleration (m/s^2) | Mass ( kg ) |
| 70 | 77.533968 | 0.2 |
| 60 | 45.572917 | 0.2 |
| 50 | 24.731086 | 0.2 |
| 40 | 7.432376 | 0.2 |
As I expected, as the power level ( and by extension the force applied ) increased, the acceleration increased proportionally. This too is in accord with Mr. Newton’s findings in regards to his 2nd Law of Motion.
Part 3.
For the final portion of the lab, I explored the Law of Conservation of Energy (Potential Energy = Mass * Acceleration * Height ). Using a height of 0.2 meters, I observed the following:
| Power Level | Acceleration | Mass | Time | Potential Energy (Joules) | Power Used (Watts) |
| 50 | 17.012821 | 0.2 | 2.173 | 392 | 180.3957662 |
| 50 | 22.135246 | 0.16 | 1.991 | 313 | 157.2074335 |
| 50 | 27.969872 | 0.14 | 1.661 | 274 | 164.9608669 |
| 50 | 42.530809 | 0.12 | 1.132 | 235 | 207.5971731 |
Further, Watts ( a unit of power ) cab be defined as an amount of energy per unit time. Therefore, by dividing the potential energy by time, I get the wattage or power used to lift the object. In simpler terms, all the weights have the same amount of work performed on them; as Work = Force * Distance, with a constant force ( 50 ) and a constant distance ( 20 cm ). Further, as power can be defined as Work / Time, we can see why as the mass decreases from 0.2 to 0.16 there is a significant drop in the amount of power used. However, as the mass of the weights used continues to drop, the time required to complete the movement decreases, thus the power required to move the weight (Work / Time ) begins to increase accordingly.