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Peer Review

One-D Motion (Displacement, Velocity, Acceleration)

by Fu-Kwun Hwang


Overall Rating:

4 stars
Content Quality: 4 stars
Effectiveness: 4 stars
Ease of Use: 3 stars
Reviewed: Jan 28, 2006 by Physics
Overview: This web page consists of two java simulations of one dimensional motion. The first applet shows the relationship between displacement, velocity, and
acceleration in one-dimensions. The acceleration can be controlled by the user through a click-and-drag protocol.

The second simulation is an inclined plane applet in which the angle of the plane can be altered. Displays show the displacement, instantaneous velocity, changes in position, and average velocity. The user is able to read data from specific points and observe the relationship between the slope of a position vs. time graph and the corresponding velocity vs. time graph along with the slope of a velocity vs. time graph and the corresponding acceleration vs. time graph.

Learning Goals: Understand graphical models of the relationships between one-dimensional displacement, velocity, and acceleration for constant acceleration. This is performed by utilizing x vs. t, v vs. t, and a vs. t graphs.
Target Student Population: Introductory Undergraduate or Advanced Placement Physics students.
Prerequisite Knowledge or Skills: Study of one-dimensional kinematics. The author uses the expressions, dx/dt and dv/dt, in the applet so the concept of instantaneous velocity and average acceleration should be discussed prior to using this applet.
Type of Material: Java applet, illustration.
Recommended Uses: Demonstration, pre-laboratory simulation, or an in-class activity.
Technical Requirements: A java-enabled web browser.

Evaluation and Observation

Content Quality

Rating: 4 stars
Strengths: The relations between acceleration, velocity, and displacement are very nicely illustrated, both graphically and through the motion of a particle. This applet can be used to help student distinguish between these three quantities, a common problem for students in introductory classes.

It is very helpful to show an inclined plane (physical diagram) along side the graphs for a ball rolling down the corresponding incline. Changing the inclined plane angle with the accompanying results is an appropriate physically intuitive approach to the problem. The display of the slope of the tangent to the velocity and displacement curves can produce a significant boost in the student's understanding. The author also shows a motion diagram of the ball on the incline.

Concerns: The first simulation shows a ball moving vertically, but the motion is not of that of an object moving under the influence of gravity. This directional cue might confuse students.

In the first simulation, the tangent lines to the velocity and position are shown, but there is no way to perform a measurement of the slope. The values are simply stated.

There is not a clear distinction between average and instantaneous velocity in the inclined plane applet. There is no explanation of the graphical display of the average velocity and why it behaves as shown. It may also be unclear to students what the red and blue lines represent on this graph and why they do not line up on either graph.

Potential Effectiveness as a Teaching Tool

Rating: 4 stars
Strengths: These applets give students a clear visualization of the linkages between displacement, acceleration, and velocity in one-dimensional motion. It allows them to explore changes in the motion that they create on their own.

This type of idea is useful in helping the students gain a qualitative (i.e.
conceptual) understanding of the relationship between, displacement, velocity, and acceleration. With the data provided on the screen, this item has the potential to combine qualitative and quantitative exercises together in one place. Interpreting graphs is also an important aspect many introductory physics courses.

Concerns: The instructions for the applet are of the form, "Try to move the mouse within the window" or "Try to change the acceleration". Students may need more specific instructions to help them determine what they should be observing.

The applet uses the somewhat unphysical model of instantaneous changes in the acceleration. Students should be given some explanation of this being a common model of more complex physical behavior.

There are no follow-up or directed questions provided to assess the student's knowledge of the material presented or identify misconceptions students may have in interpreting graphs. An instructor using this applet should take advantage of the data provided to ask students to verify values for velocity and acceleration or predict what should happen to the velocity and acceleration graphs with changes in the inclined plane. Afterwards, the students can be asked to check their predictions and record any comments.

Ease of Use for Both Students and Faculty

Rating: 3 stars
Strengths: This applet is relatively easy to learn and understand. The steps required to produce the various types of motion and subsequent observations were easily mastered.

The simulation runs within a browser window over the internet on a either a Mac or PC based operating system. With a quick demonstration this item can be used fairly easily by students.

Concerns: The instructions were somewhat nebulous and one has to invest some time to "play" with the applet to gain full appreciation of what it can do. If used by students, better directions might be needed to understand from the outset
what they are expected to accomplish with a given click and drag procedure.

On the first applet, the reset button does not set the time to zero (0) (or move the particle back to its initial positions) until the simulation starts to run again.

On the second simulation, it is not stated that the value of "Y" corresponds to the height of the incline. Also, an explanation of the meaning of the dots that appear on the screen while the ball is rolling down the incline may be useful, if "Motion Diagrams" have not previously been used in class.