This is a simulation of a hanging mass on a spring. Users may add mass or remove mass from the spring. The animation will adjust the new equilibrium point to take into account the changed mass and show the this point on a force vs. position graph. Users may also displace the mass from equilibrium and, while the simulation is running, observe the oscillatory motion and a graph showing velocity vs. position and force vs. position.
Type of Material:
Java applet simulation
Lecture/Demo, Tutorial, Homework.
Identify Major Learning Goals:
Learn about qualitative features of Simple Harmonic Motion (SHM) in the context of a mass on a spring.
Target Student Population:
High school and lower level undergraduate.
Prerequisite Knowledge or Skills:
Limited knowledge of vectors, velocity, force and position as well as the Hooke force law.
Evaluation and Observation
The plots of force and velocity vs. position, while a bit difficult for a neophyte to interpret, will provide important practice at interpreting such plots and the velocity vs. position plot can serve as a gentle introduction to phase diagrams. This applet clearly shows several of the most salient features of SHM.
The concept of the equilibrium position is a little confusing. The dy measurement is always from the current equilibrium, and can be confused with the distance from unstretched position without explanation. For the un-initiated, the graphs are unclear because the axes are not explained.
Potential Effectiveness as a Teaching Tool
For SHM, the user can see the relationship between mass and period and between period and amplitude. This is an excellent illustration of Hooke's Law. Being able to control the mass and see the displacement is good, but... (see concern)
the user cannot actually measure the displacement from the old equilibrium position to verify Hooke's Law quantitatively.
Ease of Use for Both Students and Faculty
The controls are easy to understand and manipulate.
The use of x as the vertical axis coordinate for the vertically moving mass and then plotting it as the abscissa in the plot may be a little confusing for some, but instructive. The use of a horizontal spring helps this somewhat, but also might need some explanation.
Sometimes it is difficult to control whether you are taking off mass or whether you are trying to start/stop motion.
It is unclear what all the variables labeled on the simulation are.
Other Issues and Comments:
The physics appears correct; the frequency and equilibrium displacement change appropriately for changes in mass.