The Riverboat Simulator Interactive is an adjustable-size file that displays nicely on smart phones, on tablets such as the iPad, on Chromebooks, and on laptops and desktops. The size of the Interactive can be scaled to fit the device that it is displayed on. The compatibility with smart phones, iPads, other tablets, and Chromebooks make it a perfect tool for use in a 1:1 classroom.

This Interactive provides an outstanding preface to understanding the motion of a projectile. The Interactive models the motion of a riverboat heading across a river in the presence of a river current. Learners can modify the speed and direction of the boat, the speed at which the water moves (i.e., the current) and the width of the river. The crossing time and the downstream distance are displayed. As such, the simulation provides a variable-rich environment for investigating the effect of a the river's current upon the boat's motion.

The simulation serves two main roles in a physics curriculum. The first role is that it provides an introduction to and a lesson in the topic of relative velocity. The boat moves relative to the water and the water moves relative to the shore. The resulting motion is the combination of these two components of motion. Teachers can use the simulator in either demonstration mode to lead a discussion on the topic of relative velocity or by providing a question for students to explore or an activity for them to complete.

It is the second role of this simulation that gets us most excited about it. The role provides a great introduction into the concept of the independence of perpendicular components of motion. Changes in the river velocity have no effect upon time to cross the river. Put another way, we could say that the vertical component of motion (the river's current) has no effect upon the horizontal component (the boat velocity and the time to cross the river); this independence of perpendicular components of motion is quite obvious if students' restrict their exploration to cases in which the boat*heads* straight across the river. The principle is the independence of perpendicular components of motion is essential to understanding the motion of a projectile. In projectile motion, the horizontal velocity of the projectile has no effect upon the time it takes the projectile to fall vertically. Similarly, the vertical force of gravity has no effect upon the horizontal motion. The independence of these two perpendicular components of motion for projectiles are much more believable to students once they have observed the concept in a riverboat problem.

The simulation serves two main roles in a physics curriculum. The first role is that it provides an introduction to and a lesson in the topic of relative velocity. The boat moves relative to the water and the water moves relative to the shore. The resulting motion is the combination of these two components of motion. Teachers can use the simulator in either demonstration mode to lead a discussion on the topic of relative velocity or by providing a question for students to explore or an activity for them to complete.

It is the second role of this simulation that gets us most excited about it. The role provides a great introduction into the concept of the independence of perpendicular components of motion. Changes in the river velocity have no effect upon time to cross the river. Put another way, we could say that the vertical component of motion (the river's current) has no effect upon the horizontal component (the boat velocity and the time to cross the river); this independence of perpendicular components of motion is quite obvious if students' restrict their exploration to cases in which the boat

The Physics Classroom has also prepared two different exercises for the use of this Interactive in the classroom. The first exercise is considerably more open-ended and naturally addresses several of the Science and Engineering Practices of the Next Generation Science Standards. The exercise challenges students to use this variable-rich environment to explore a complex question. Little direction is provided as to how to design the study. The exercise can be completed quite quickly by a typical high school science class. We recommend pairing students for completion of the exercise. The resulting dialogue of two students focused on the same question is a profitable dialogue. We also recommend using this first exercise as a type of "lab test" in which students are on their own to answer the question with little to no assistance from the teacher or other student groups. This "test-like environment" allows the teacher a chance to observe the ability of their students to experiment with a testable question.

The second exercise is considerably more guided and serves the role of helping students to understand the application of vectors and relative velocity principles to the context of a riverboat moving across a river in the presence of a current. The exercise is lengthier and more time-consuming. It provides a stronger connection to vector principles than it does to projectile principles.

There are numerous resources at The Physics Classroom website that serve as very complementary supports for the Riverboat Simulator Interactive. These include:

- Reading:

Lesson 1 of the Motion in Two Dimensions Chapter of the Tutorial is a perfect accompaniment to this Interactive. The following pages will be particularly useful in understanding relative velocity and the independence of perpendicular components of motion:

Relative Velocity and Riverboat Problems

Independence of Perpendicular Components of Motion

- Minds On Physics Internet Modules:

The Minds On Physics Internet Modules include a collection of interactive questioning modules that help learners assess their understanding of physics concepts and solidify those understandings by answering questions that require higher-order thinking. Assignment VP6 of the Vectors and Projectiles module provide great complements to this Interactive. They are best used in the middle to later stages of the learning cycle. Visit the Minds On Physics Internet Modules.

- Curriculum/Practice: There is a single Concept Development
*think*-sheet at the Curriculum Corner that would be very useful in assisting students in cultivating their understanding. It is named

Relative Velocity and Riverboat Problems

Visit the Curriculum Corner.

Additional resources and ideas for incorporating the Riverboat Simulator into an instructional unit on Vectors and Projectiles can be found at the Teacher Toolkits section of The Physics Classroom website. The Vectors Toolkit provides some exceptional support from various websites found on the Internet. Visit Teacher Toolkits.

The Physics Classroom would like to extend a special thanks to Nerd Island Studios for the creation of this HTML5 Interactive. Visit http://www.nerdislandstudios.com to see more great stuff by Nerd Island Studios.