Introduction to physics

[krmatt1]

I am an experienced programmer but am not familiar with the basic concepts behind rigid body physics. Reading the Chipmunk documentation, I see a lot of terms I am unfamiliar with - moments of inertia, torque and so forth. Can anyone point me toward a "rigid body physics 101" type resource?

[slembcke]

Hmm. Not really, I learned it all the hard way and Google isn't really helping either. The wikipedia pages for most of those terms are as abstract as ever too.

I guess I could make an introduction that would be helpful to a lot of people. How about a quick glossary for now.

• Rigid Body: A solid object that doesn't change shape when it collides. Think like an object made of unbendable, unbreakable steel.
• Mass: How strongly an object resists forces being applied to it. i.e. An object with more mass needs a bigger force to accelerate it at the same rate as an object with less mass. Not to be confused with weight as an object has no weight without gravity, but it still has mass. Weight is the acceleration due to gravity multiplied by the mass.
• Center of Gravity: Also sometimes called the center of mass. The balancing point of an object. In Chipmunk, the position of a rigid body is always it's center of gravity, and the rotation always happens around the center of gravity.
• Moment of Inertia: Think of it as the rotational mass of an object. The higher the moment is, the harder it is to cause the object to spin around it's center of gravity.
• Torque: Think of this as a rotational force. When torque is applied to a rigid body, it will cause it to spin around it's center of gravity.

Is that a good starter list? Anything else?

[krmatt1]

Thanks. I'll keep chugging away.