# Homework Help: Some materials properties

1. Oct 19, 2012

### RicardoTk

Hi everyone!

Im developing an application with a physics library.

In the application I pre-setted some materials with the following properties,

Density, Friction and Restitution

Im not sure if this informations are truly trustable,

Can you guys just review this for me?

===|Wood|==
Density: 680 kg/m³
Friction: 0.4
Restitution: 0.7

===|Iron|==
Density: 7400 kg/m³
Friction: 1 (Steel = 0.8 )
Restitution: 0.85

===|Concrete|==
Density: 2300 kg/m³
Friction: 0.65
Restitution: 0.75

===|Rubber|==
Density: 920 kg/m³
Friction: 0.75
Restitution: 0.3

===|Polystyrene|==
Density: 80 kg/m³
Friction: 0.5
Restitution: 0.5

===|Plastic|==
Density: 1300 kg/m³
Friction: 0.35
Restitution: 0.6

References:
http://www.matbase.com/
http://www.matweb.com/
http://physics.info/density/
http://www.bulletphysics.org/Bullet/php [Broken] ... ?f=9&t=616
http://www.woodweb.com/knowledge_base/W [Broken] ... dbook.html
http://www.engineershandbook.com/Tables ... cients.htm
http://www.engineeringtoolbox.com/frict [Broken] ... d_778.html
http://hypertextbook.com/facts/2006/restitution.shtml

Thanks!

Last edited by a moderator: May 6, 2017
2. Oct 20, 2012

### frogjg2003

I can't tell you if these values are correct, but the coefficient of friction and (probably) the coefficient of restitution are not intrinsic properties of the materials. Think about it, the same rubber tires will stop in a shorter distance on dry asphalt than on wet, and a basketball will bounce higher on cement than on shag carpeting.

3. Oct 20, 2012

### CWatters

How accurate do they need to be because the properties for wood vary by a factor of at least 2 depending on species.

4. Oct 23, 2012

### RicardoTk

Thank you guys!