Peer Review

Free Fall Lab - Terminal Velocity

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Overall Rating:

Content Quality:

Effectiveness:

Ease of Use:

Overview:: This is a Shockwave applet that simulates a falling object under the influence of gravity, air resistance, and bouyant force. Users can control the object's mass, radius, the height of the drop, wind speed and air density. The time step used for internal calculations can also be varied. Position, velocity and acceleration are displayed graphically. Cooridinates of points on the graph can be read out by moving the mouse over them.

This material has become for-fee. See comments below.
Type of Material:: Shockwave applet simulation
Recommended Uses:: Lecture/Demo or Student Activities
Technical Requirements:: The Shockwave plug-in (available free from Macromedia) is required to run this applet.
Identify Major Learning Goals:: To learn about the behavior of falling objects, both with and without air resistance.
Target Student Population:: High school and lower level undergraduate. Could be used for upper level undergraduate courses studying air resistance.
Prerequisite Knowledge or Skills:: Users should know the relationships between position, velocity, and acceleration and should be able to interprete graphs.

Rating:
Strengths:: Overall, this is a very fine effort. Allowing the user to vary air resistance by varying the air density was an excellent idea. The applet also includes an option to turn bouncing on and off, this makes it possible to invesitgate coefficients of restitution.
Concerns:: The ability to set the initial velocity would be of far greater use than setting a wind speed. The readouts from the graphs are not very accurate -- certainly nowhere near the "significant" figures shown. For some reason, the acceleration due to gravity seems a little high. With no air resistance, the acceleration appears to be 10.1 m/s².

Rating:
Strengths:: This is an excellent simulation of a falling object. The breaking glass sound effect (with bouncing off) is a wonderful touch.The applet is flexible enough for the student to study falling objects under a variety of conditions.
Concerns:: The learning effectiveness of the applet is highly dependent upon the assignments that need to accompany it, or if used as a demonstration, the ability of the lecturer to actively involve the students by requiring predictions or other techniques. The inaccuracy of the graph readouts may make quantitative assignments of limited value.

Rating:
Strengths:: The interface is very intuitive. Also, most of the parameters that affect the fall when air resistance is a factor (mass, cross-sectional air, and air density can be varied, as can the drop height. This makes it possible to use the applet in a wide variety of ways. Sequential trials can be simultaneously displayed to help the student identify effects of changing parameters.
Concerns:: The force due to the air includes both air resistance and bouyant force. These effects cannot be separately studied, except through detailed calculation. Although this better reflects the real situation, it places an unnecessary complication in the way of student understanding of this type of motion. To use this item effectively as homework, the instructor will need to write thoughtful assignments.

Other Issues and Comments:: The versatility of this applet makes it useful for students at a number of different levels, from non-science majors to physics and engineering majors.

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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