Energy on an Incline Lab
Resource Downloads
The Following Information is Provided to the Student
Question: What is the total amount of mechanical energy for a cart moving along an incline plane at five different locations? How do the results compare to the expected results?
Purpose: To determine the total amount of mechanical energy of a cart on an inclined plane at five different positions and to compare the results to the expected results.
A complete lab write-up includes a Title, a Purpose, a Data section, and a Conclusion/Discussion. The Data section should include the provided table. Work must be shown for the KE, PE and TME calculations. The energy bar charts should be completed. The Conclusion/Discussion should include a comparison of the total energy at the five positions and a generalization about the principle which the data support. An error analysis should be conducted in which the expectations are discussed; the degree to which the data align with the expectations should be described. Averaging and percent differences should be used.
Scoring Ruberic
| E7. | Energy on an Incline Lab | Score |
|---|---|---|
| _____ | Included, labeled and organized all parts of the lab report. | _____ / _____ |
| _____ | The Data section includes the provided table. Work is clearly shown for the KE, PE and TME values. Data is reasonably accurate; all measurements were made after the initial push. Energy bar charts are correctly completed. | |
| _____ | Conclusion/Discussion describes the energy at the five positions. Discussed expectations regarding the energy values and discussed the degree to which expectations matched the results. Might have averaged all TME values and calculated percent differences. Discussion reveals understanding. |
Lab Details
Materials Required
Cart; track; computer-interfaced motion detector; lab poles; clamps; meter stick; mass balance.
Description of Procedure
A track is inclined by propping it up on one end using a lab pole and clamps. A motion detector is placed at the elevated end of the track. A cart is given a quick push from the bottom of the track, imparting to it an initial amount of kinetic energy. The cart travels up the track, slows down, turns around and accelerates back down the track. Students view the plot of the cart's position and velocity with respect to time on the computer. Five positions along the trajectory are chosen. The speed of the cart and the distance from the motion detector are read from the plots for these five positions. The cart is then placed along the track at the measured distance from the motion detector and a meter stick is used to measure the height above the tabletop for this position. Kinetic, potential, and total mechanical energy values are computed for the five positions along the track.
Safety Concerns
There is always a higher than usual level of risk associated with working in a science lab. Teachers should be aware of this and take the necessary precautions to insure that working environment is as safe as possible. Student horseplay (especially the use of meter sticks as swords) and off-task behaviors should not be tolerated.
Suggestions, Precautions, Notes
- Before running any trials, students should practice giving the cart a push so that it travels up the track to a peak position near the top of the track and just prior to colliding with the motion detector.
- One student should be assigned the sole task of being the body guard of the motion detector. If trouble is foreseen, they should throw their body (or at least their hand) between the speeding cart and the motion detector. Likewise, the student who pushes the cart should be assigned the task of catching it at the bottom of the track before it crashes into the table or the floor.
- Inform students to select five positions for analysis - one position should correspond to the highest point along the cart's path; two positions should correspond to when the cart is traveling upward and two positions should correspond to when the cart is traveling downwards.
- Caution students to not select as one of their five positions a position which corresponds to the pushing phase.
- If a greater challenge is desired, do not provide a lot of details about how the height is determined from the distance away from the motion detector.
Links
Connections to The Physics Classroom Tutorial:
The following readings are a suitable accompaniment to this lab:
http://www.physicsclassroom.com/Class/energy/u5l2bb.cfm
http://www.physicsclassroom.com/Class/energy/u5l2bc.cfm
Connections to Minds on Physics Internet Modules:
Sublevels 7 and 8 of the Work and Energy module are a suitable accompaniment to this lab:
https://www.physicsclassroom.com/minds-on/work-and-energy