## Before You Start

Assigning Physlet Physics or Physlet Quantum Physics material without properly preparing the class can lead to frustration. Although Physlet problems often appear to be simple, they are usually more challenging than traditional problems because novice solution strategies are often ineffective. In addition, small technical problems are bound to occur without testing. We use Physlets extensively in our introductory courses at Davidson College, but we always start the semester with a short laboratory whose sole purpose is to introduce the Physlet user interface and to solve a Physlet problem in the way a physicist solves a problem; that is, to consider the problem conceptually, to decide what method is required and what data to collect, and finally to solve the problem. As a follow-up, we then assign a simple Physlet-based exercise that must be completed in one of the College's public computer clusters. This minimal preparation allows us to identify potential problems before Physlet-based material is assigned on a regular basis.

In response to these possible difficulties, we have written Chapter 1: Introduction to Physlets. This chapter provides students and instructors with a guided tutorial through the basic functionality of Physlets. It is important to emphasize that:

• Physics are almost always simulations, not animations, that solve a mathematical model and the simulation will reflect the model's assumptions and not the real world. For example, mechanics models may, or may not, include the effects of friction and optics models use the small angle approximation for lenses and mirrors. These assumptions are stated in the narrative.
• Physlets usually output numbers, not symbols such as units. When units are required, they are stated in the narrative.
• Physlets almost always require that the student or teacher interact with the simulation. If the narrative asks about the position of an object, the user can click-drag with simulation to measure an objects coordinates. Objects in some simulations can be repositioned by click dragging on the object. Note that the cursor will change if an object is draggable.
• Many simulations have input fields that accept a number or a simple mathematical expression, such as 2*pi. The user must, however, press the [Enter] key after entering a new value. The input field will show a red background if the entered value is incorrect and a white background if the entered value has been accepted. If the input field in an initial condition, the user should reset the the time to rerun the simulation.
• If a simulation becomes hopelessly confused because of invalid or unrealistic initial values, reloading the html page will usually clear the problem.
• You are not alone. Ask questions, reports bugs, and suggest Physlet-based supplemental material on the OSP-ComPADRE Physlet discussion forum.

After completing the exercises in Chapter 1, students and instructors alike should be in a position to complete the exercises in the Physlet Physics and Physlet Quantum Physics books.