## Three Physics Examples - "getting the physics right" plus a little more

Extras...

• The GPS unit, theory and practice*
• Polygon tool - cute little application to make polygons*
• Two Flash tutorials below

*To use the applcaitons below you will need the Flash 6 or greater player plug-in to your browser. The Flash player is available for free from Macromedia

Animations in Flash. There are basically two ways to create animations with Flash: (1) using the Flash engine for linear interpolation of an object between two positions, and (2) pixel-by-pixel control of the object position by exact movie clip commands. [ mc._x (mc._y)] Using pixel controls, it is possible to manipulate an object's position with virtually unlimited bounds.

Here are links to four physics Flash animations. In each case they are not "complete" commercial products. Rather they are starter examples to show what can be done with FLASH programming technology. Flash programming can be accomplished at various levels, from really quite simple animations to complex physical reality. With Flash, links to JavaScript, Java, and server-side applications are very much possible. Indeed, one can think of Flash as the graphics front-end to comprehensive numerical examples.

### Bouncing ball

The bouncing ball. Using Flash it is possible to make an object go up and down. But it is important that the physics should be right. Teaching a concept visually using incorrect animations yields students that have profound physical misconceptions. Here are three examples. The first is an object that goes up and down with "linear physics". The second uses the easing feature of Flash to mimic the acceleration of gravity. The third uses the actual law of gravitation.

 Up and down with linear motion. Source Up and down with fake physics. Source Correct physics - multiple gravities and damping. Source

Works in Flash 5.

### Pendulum

The second example, the pendulum allows pendular but not perfect pendular motion. One can change the period but not the length of this pendulum. Also, there is a timer. It is possible to devise virtual "physics" experiments with this animation. In fact a science fair type project could be accomplished with such a tool.

 Pendulum with damping and mouse control of the initial position.

Works only in Flash 6.

### Projectiles

In this third example, we show two projectiles which can be thrust from a specified angle with a specified velocity. Shown are the times to hit the ground and the maximum height.

 Projectile with angle and initial velocity input and with time at touch down, maximum height and horizontal distance travelled. Source

Works in Flash 5.

### Planetary motion

In this example, we show simple elliptical motion about a "sun". In the first example, there is a single planet. In the second, the user can select multiple planets, creating an entire pseudo solar system. The physics here is all wrong.

 One Planet. The user has no choices except to start the motion. (Source) Here is a tutorial on how to make this Movie. Multiple Planets. Tthe user has no choices except to select the number of planets and to start the motion. The radii and frequencies of the "planets" are generated randomly. (Source) Three dimensional perspective of the earth circling the sun with stars blinking.

Works in Flash MX.

### Summary

In each of these problems, getting the physics right requires some considerable extra effort beyond the rather powerful but intuitive animation features of Flash.

Tutorial on making a Tween motion. Source.
Tutorial on using ActionScript to make elliptical motion. Source
To obtain source files right-click on link and select save.

Modified.

### GPS Units on the plane

A GPS unit is a receiver that obtains the distances from and the coordinates of a number of satellite. The graphic is shown below

As you can see multiple signals are obtained in order to obtain the exact location. We have two lessons on the GPS unit and a FLASH movie for you to experiment with a planar GPS unit.

What is the GPS and how does it work?

The Planar GPS, theory and application.

To use the applcaitons below you will need the Flash 6 or greater player plug-in to your browser. The Flash player is available for free from Macromedia