I have little problem - don't work friction for circular bodies. I create horizontal ground and add circular body with a little LinearVelocity for example myBody:setLinearVelocity( 10, 10). Friction my ground friction=1.0 for body friction=1.0 this mean that my body must stop very fast, but nothing happen BODY NEVER STOP!!! For rectangular and polygon body friction work great. I try create my circular body as polygon body, but it's not very good it's look like polygon and I want circular body. Then I try use linearDamping - yes it work, but I want use friction ( I have ground and other object with different friction and for me very important how interact this circular body with my body with different friction )and I thing if we all have for param for circular body as friction they must be work or write on api that this parametr don't work for circular body. if you don't have time You can don't write any example and try this in \Sample Code\Physics\EggBreaker - remove all object leave only grass and boulder - set all friction 1.0 and add for boulder little LinearVelocity - body don't stop!!!