public void getLinearVelocity(Vector3f vec) {
        Converter.convert(rBody.getLinearVelocity(tempVec), vec);
    }
Get the current linear velocity of this PhysicsRigidBody
@param vec the vector to store the velocity in
jme3-jbullet/src/main/java/com/jme3/bullet/objects/PhysicsRigidBody.java