This is a simulation of a 2-dimensional collision between circular objects of finite radius. The impact parameter is adjustable by changing the direction of incoming velocities. The radius of the circular objects and the coefficient of restitution for the collision are also adjustable. One may observe the collision in one of four frames of reference, the lab, the center-of-mass, and the frame of either of the two objects.
Type of Material:
Java Applet Simulation
Recommended Uses:
Lecture Demo or as a building block for an assignment.
Technical Requirements:
Java enabled browser.
Identify Major Learning Goals:
Students running this simulation should obtain a qualitative and quantitative understanding of how objects of the same mass interact during a 2-D collision. The implications of momentum conservation can be investigated.
Target Student Population:
Secondary and lower division physics
Prerequisite Knowledge or Skills:
Introduction to collisions, momentum, and energy.
Content Quality
Rating:
Strengths:
This simulation functions well for all elastic collisions. It includes velocity vectors (with components parallel and perpendicular to the collision). The ability to adjust the parameters for the collision is important for student investigations.
The collision can be represented in one of several frames of reference giving students a better concept of conservation laws and center of mass.
Concerns:
The mass ratio is adjusted by changing the radii of objects. It is not clear from the instructions what physical parameters are being adjusted to affect the mass ratio.
The objects are of finite size and rotational effects are not included. This results in unphysical results for off center collisions when the coefficient of restitution is set to zero. This is a minor issue because the simulation is not meant to study rotational effects.
Potential Effectiveness as a Teaching Tool
Rating:
Strengths:
The parameter controls on relative masses, initial velocities, and initial position makes the simulation useful for virtual experiments.
The user can stop the simulation, to measure differences in velocity vector components before and after the collision, or can watch a continuous collision.
Concerns:
Students will need guidance to effectively use this applet because of the many possible parameter settings.
The coefficient of restitution is a parameter that is not introduced in most introductory physics texts. Instructors may need to introduce this.
It is difficult to easily set-up the same collision in different frames of reference perspectives.
The simulation has the boundaries connected so that an object leaving the left side enters back on the right. This should be pointed out to students. This limits the amount of the trajectory that is observable after the collision.
Changing the radii of the objects in order to change the mass ratio invites confusion between density and mass of an object.
Ease of Use for Both Students and Faculty
Rating:
Strengths:
This simulation has intuitive controls.
The objects are large enough to easily see the collision surfaces and vectors. All velocities and positions are shown by coordinates and are easily adjustable.
Concerns:
The user can not easily change the perspective from one frame of reference to another for the same collision. There are no edit boxes to manually enter parameter values which would make repeatability of a collision easier.
The program doesn't prevent changing parameters to unusable values. For example, the user can change the radii of an object so that it overlaps the other object or obscures the entire viewing region.
Other Issues and Comments:
This is a reasonably solid applet that would be most useful as a building block for an assignment.
Creative Commons:
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