Peer Review

2D Collisions

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Content Quality:

Effectiveness:

Ease of Use:

Overview:: Shockwave simulation allows users to explore collisions between two pucks on a virtual air table. The initial parameters can be changed (mass, directions, speeds). The collision can be made elastic, perfectly inelastic or "magnetic". Other features allow for limited measurements to be made, a ruler allows for distances and angles. The tilt of the table can also be adjusted.

This material has recently become for-fee. See comments below.
Type of Material:: Shockwave applet
Technical Requirements:: Requires shockwave plugin.
Identify Major Learning Goals:: To help students understand the physics underlying collisions.
Target Student Population:: Secondary, or Lower/Intermediate level undergraduate
Prerequisite Knowledge or Skills:: None for qualitative demonstration. To use quantitatively the user will need algebra and knowledge of conservation of momentum applied to collisions.

Rating:
Strengths:: For qualitative use the simulation does a very good job of displaying different types of results that may occur. It allows one easily and quickly to set all of the relevant collision parameters using the mouse, and requires students to take measurements to determine final velocities. The applet is a versatile component that can be used with instructor-supplied content to help students understand momentum conservation.
Concerns:: Although there is a checkbox labeled "Inelastic", in fact, it should be labeled "Perfectly Inelastic". The applet needs documentation to describe how to set parameters. (The various ways of using the mouse are clever, but not obvious to inexperienced users.)

Rating:
Strengths:: Recommended Use(s) for Material: Lecture/Demo, Lab, Homework (instructors must make out assignments)

A variety of two dimensional collision situations can be examined. Answers are not simply given to students; they need to make measurements to check their calculations. The perfectly inelastic collision cases qualitatively show conservation of angular momentum, including the "wobbling" of a rotating system of large mass with an attached small one.
Concerns:: No preset activities are included with this simulation. The learning effectiveness will be strongly dependent upon the lessons created by the instructor.

Rating:
Strengths:: The applet has a lot of flexibility built into it, and can be used to build a variety of assignments. A snapshot with trails can be copied to the clipboard for examination. Thus a single collision can be copied and distributed for analysis. The ruler allows for measurements to be made on the simulation.
Concerns:: Instructors are required to create their own assignments as well as instructions for using the applet. The lack of a more general inelastic collision setting leaves a hole in an otherwise excellent tool for studying momentum conservation. Only 20 data points displayed on trails, which is insufficient in some cases. The meaning of "spark frequency" and "Delta T" is not clear (they seem redundant), the user must discover the difference. Setting particular velocity values is difficult to do precisely. Finally, since there is no indication of initial positions, the impact parameter cannot be accurately measured.

Other Issues and Comments:: Access to this material has recently become by subscription. Although the MERLOT/Physics does not usually review for-fee materials, this review will remain available for our users.
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