This is a simulation of a boat traveling across a moving river. The user can adjust the speed of the water current as well as the magnitude and direction of the boat's velocity relative to the water. Color-coded vector arrows are displayed and represent the magnitude of the current's velocity as well as the velocity of the boat relative to the water and to the shore.
To help determine the resulting velocity of a boat that travels across a river using vector addition, namely the headtotail method.
Target Student Population:
High school and lower-division undergraduate.
Prerequisite Knowledge or Skills:
Backgrounds in velocity and vector addition, namely the headtotail method.
Type of Material:
Java simulation in a browser window.
Preclass or inclass demonstrations, reinforcement of material discussed in class by the Instructor, student assignments. Perhaps students could check their homework problems.
A web browser such as Internet Explorer that supports Java.
Evaluation and Observation
The content is good. This applet has a very narrow focus, however, given its limited intent it does a very good job. The size and direction of the velocity vectors is accurate.
Explanatory text supplied with the applet is very terse; if it is used as a student exercise instructors will need to supplement this.
Potential Effectiveness as a Teaching Tool
This applet is an excellent method for illustrating how the direction of the relative velocity can be determined from vector addition. It helps students spiral back and apply vector addition for a physical problem different from what was probably used to introduce vectors. The color coded arrows help the user to distinguish between several very different, but related, vectors.
Numeric values are used to input velocities, however, the only numeric results in the output are the x and y coordinates of the boat. Also, the resultant vector is always displayed; it might be more effective from a pedagogical standpoint if the resultant vector were not shown until the boat begins to move across the river.
Ease of Use for Both Students and Faculty
The author provides a little background; however the simulation is rather selfexplanatory for the most part. There are only three (3) variables that can be changed. The Java application downloads in just a few seconds. The lines are coloredcoded to distinguish between the velocity of the river, velocity of the boat, and the relative velocity of the boat with respect to an observer on the ground (i.e. bank). The speed of the river and boat, along with the initial direction of the boat, can be adjusted easily with a slider bar.
Instructors desiring to use this applet for student assignments will need to provide additional explanations of the physics if students are to get the most out of it.
Other Issues and Comments:
This is one applet in a collection of several dozen similar resources developed by the author. These all are focused simulations that consider a single physical situation.