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# Peer Review

## Ratings

### Overall Rating:

Content Quality:
Effectiveness:
Ease of Use:
 Reviewed: May 31, 2006 by Physics Overview: This simulation allows the user to apply forces in one dimension to a variety of objects and observe the resultant motion. The simulation starts, by default, with friction included, but the user may investigate dynamics without friction. There are displays showing force, acceleration, velocity and position vs. time graphs as well as a free body diagram. The user can change the effects of gravitational force, friction coefficients, masses, and applied forces. Learning Goals: This applet is designed to help the user understand the relations between "applied" force, net force, and motion (position, velocity, and acceleration) as well as the difference between static and kinetic frictional forces. Also, it can be used to explore Newtons 1st and 2nd laws of motion in one dimension. Target Student Population: Students enrolled in any introductory high school or undergraduate college physics lecture and/or laboratory class. Some aspects might be suitable for physical science classes at the middle school level (or later). Prerequisite Knowledge or Skills: General introductions to forces and kinematic quantities are most likely necessary. Previous work with force diagrams, Newtons 1st and 2nd laws of motion, and vector addition will be helpful. Type of Material: Java simulation. Recommended Uses: Lecture demonstration material or homework assignments as well as virtual laboratory exercises. Technical Requirements: This is a standalone Java application that requires Java Web Start 1.4 or better to run.

### Content Quality

Rating:
 Strengths: The content of this simulation is excellent. The results of the simulation for experiments such as determining the maximum static frictional force, the kinetic frictional force, and accelerations agree with calculations. The frictional force changes appropriately from static to kinetic when objects start moving, and similarly when they stop. The simulation allows for investigation of a diverse set of properties relating to friction, applied force, motion graphs, and mass. A free body force diagram is shown; the applied force can be varied, as can the mass of the object, gravitation, and friction coefficients. The results are shown as graphs of force, acceleration, velocity, and position vs. time. A user can also record, playback, and investigate a simulation run. Concerns: The free body diagram in the simulation includes a vector for the total force. In many textbooks it is recommended that this not be done.While the user can examine a wide variety of parameters relating to applied and friction forces, the simulation results can go significantly outside the range of data that can be displayed. For example with a small mass and large force, several of the plots rapidly go off scale for any allowed scaling. Users should be aware of these limits and know how to clear the simulation and re-start.

### Potential Effectiveness as a Teaching Tool

Rating:
 Strengths: This applet is very good at showing how the static frictional force varies between zero and some maximum value as an applied force increases, and that the maximum is where the object starts to move. This and the difference between static and kinetic friction are both points where students often struggle. The use of graphs to display results emphasizes the importance for students to understand graphical representations of data.This applet is quantitative, so students can either predict results before a virtual experiment or check their results of the simulation. This can be done for both static experiments and those where the object is moving. The graphical nature of this applet is also very compelling for making qualitative observations. Concerns: Without scripted activities, students may encounter some confusing or frustrating results. For example, it will be difficult to replicate the standard switchover plot from static to kinetic friction with a linearly increasing applied force. The manual controls of the applied force are difficult to vary smoothly.The scope of this applet is somewhat limited as it includes only 1D motion, applied forces, and friction.

### Ease of Use for Both Students and Faculty

Rating:
 Strengths: The simulation is easy to use. A wide variety of controls have been included for users. The ability to stop, re-start, and play back the simulation increases the possibilities for using the simulation. Concerns: The screen is crowded, particularly with multiple graphs displayed. While the user has the option of viewing only one of the various time plots at a time, there can still be problems. The force graph must be displayed if the user is to have manual control of the applied force using the slider. Depending on the selection of displayed material, the controls for rescaling the plots are in the way of text. If all four plots are displayed, the labels overlap.In the illustration of the experiment, the friction force label is displayed on top of the applied force in the case that they are in the same direction, making it somewhat difficult to distinguish the two.

Other Issues and Comments: This simulation is part of a growing collection created by the Physics Education Technology Group. These materials are designed based on research in physics education and studies of student usage of the simulations. Information about the results of research on the impact of the simulations and a database of instructor-submitted lesson plans are available on the web site.
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