Phun is a fun 2D physics simulator/game, where you enter simple situations, interact with them, and see the results instantly. I will be showing how to make games in Phun that demonstrate laws of physics. BR BRNote on formatting: BRSub-window names are italicized.

Download & Install

Go to [http://linux.softpedia.com/progDownload/Phun-Download-36405.html].

Game 1: Racing

BRFirst we will make a monocycle. This lesson will teach students about gravity and inertia.

Step 1

BRChange the settings. At the top of the screen should be a sub-window called Options. If this is not there, click on the options button in the Phun beta sub-window. BRThe following should be on:

• Draw Hinges/Fixes when running
• Gravity
• Air Friction
• Draw Inside Objects

The rest are relatively insignificant. Go to File... > Clear scene

Step 2

Make the racing surface. BRSelect the Plane tool from the Toolbar. Pick a point in the lower one-forth, drag your mouse straight up and let go. BRYou should have a ground now.

Step 3

BRMake the monocycle! BRStart by drawing a circle with the circle tool near the ground. BRDraw a box using the box tool. Start below the bottom of the circle and to the right of the center of the circle and go to the left of the center of the circle and a little above the center of the circle. The box should hang down from the center and protrude. BR[attachment:Monocycle-Pendulum.png Example]

Step 3.1

BRMake the motor on the monocycle. Right-click on the circle, go to Geometry settings>Add center hinge. Right click on the hinge and go to Hinges> BRCheck the following:

• Motor
• Control with arrow keys

[attachment:Monocycle-motor-checking.png Image]

Testing

BRPress space to test it. BR BRDon't worry if it's gone. BRActually, it isn't. It just flew up so fast that you couldn't see it. Why? The pendulum was hanging down into the ground. The fastest way to remove that was to fling it straight up. (To see the flung moncycle, right-click anywhere on the screen where there isn't any objects. Use the pan and/or zoom to find it.) BR(If the pendulum hangs inside the circle, that's OK. Just follow these instructions anyway to learn about collisions in Phun.) BR BRTo go back to the editing screen press Ctrl-Z or click Undo Sim Start in the Control window. BR(If you Panned/Zoomed before, Pan/Zoom back.)

Step 4

BRRight-Click on the pendulum. Go to the Collision menu... > BRUn-check all boxes. BR[attachment:Monocycle-Pendulum.png Image]

Testing

BRPress space to start. BR BRPress the left arrow key. The pendulum should move left, followed shortly by the cycle. BRPress the right arrow key. The pendulum should move right, followed shortly by the cycle. BR BRIsn't very interesting though, is it? Let's add an AI player. (Actually, the intelligence part of artificial intelligence is kind of a stretch.)

Step 5

BRMake the AI player. BR BRSelect the brush tool, and draw a closed shape around the mono cycle. The monocycle should be flashing now. Go to the Options window and un-check Draw inside objects. Hold down Control and drag the monocycle until the two monocycles do not intersect. Right click on the hinge of the AI player. Go to Hinges... > BRUncheck Controlled by arrow keys.Monocycle-RPM-change.png BRRight-Click your monocycle body. Go to Collision Menu... > BROnly Check:

• Collision group A

Right-Click the AI's monocycle body. Go to Collision Menu... > BROnly Check:

• Collision group B

You now have a controllable monocycle plus one to race against. BR BROptional: Make things more interesting by setting the speed of both hinges to 45 rpm instead of 15. [attachment:Monocycle-RPM-change.png Image]

Game 1 questions

Newton's Laws:

• Newton's First Law states that an object will remain at rest or in uniform motion in a straight line unless acted upon by an external force.
• Newton's Second Law:

  F_{orce (newtons)} = M_{ass (kilograms)}xA_{ccelleration (meters/second/second)} This relates to the amount of force acting on an object. (Note: Obviously, the acceleration is is the same direction as the force.) Example: You pull a 1KG (2.2 pounds) weight across a frictionless floor where there is no air resistance with a force of 1 newton, it accelerates at 1m/s/s (2.24 miles/hour/second). This means that at second zero it isn't going anywhere. At second one it is going at 2.24 miles an hour. At second two it is going 4.48 miles an hour.

• Newton's Third Law states that every action has an equal and opposite reaction.

Identify and answer:

When the pendulum is rotating clockwise, what direction is the wheel rotating? Counter-Clockwise What law is in action? Third

If you take your hand off the keys while the cycle is moving, it stops (eventually). Why? Friction What law is in action? First

Bibliography

Newton's Laws: [http://hyperphysics.phy-astr.gsu.edu/Hbase/Newt.html] BRMore about Phun: [http://www.acc.umu.se/~emilk/]