Dynamics Properties Rollout

Bounce Coefficient—Sets how far an object bounces after hitting a surface. The higher the value, the greater the bounce. A value of 1 represents a "perfectly elastic collision," or a bounce in which no kinetic energy is lost. Default=1.0.

If you've seen the desktop toy with four ball bearings swinging back and forth on strings and hitting one another, you've seen an example that comes very close to a bounce coefficient of 1. Generally, hardened steel or a super ball have a bounce near 1, while lead has a bounce near 0.

Static Friction—Sets how difficult it is for the object to start moving along a surface. The higher this value, the more difficult. Default=0.0.

If something weighs ten pounds and sits on Teflon (a static friction of near 0), it takes almost no force to make it move sideways. On the other hand, if it sits on sandpaper, then the static friction might be very high, on the order of 0.5 to 0.8. A static friction near 1 is very difficult to create in the real world without adhesives or friction material.

Sliding Friction—Sets how difficult it is for the object to keep moving over a surface. The higher this value, the more difficult for the object to keep moving. Default=0.0.

Once two objects begin to slide over one another, static friction disappears and sliding friction takes over. Generally, sliding friction is lower than static friction due to surface tension effects. For example, once steel starts sliding over brass (a value of static friction that might run from 0.05 to 0.2), the sliding friction drops to a significantly lower value, on the order of .01 to 0.1. For some materials, such as specific friction materials like brake linings, sliding friction is just as high as static friction because it is used in conjunction with a nearly frictionless material such as hardened polished steel.