diff --git a/Engine.h b/Engine.h
index 8f6001d..5e2722a 100644
--- a/Engine.h
+++ b/Engine.h
@@ -68,8 +68,9 @@ class Engine
                     render();
                 }
                 void setTexture(GLuint tex);
-
                 void draw();
+                dReal getMass() { return m_ode_object->getMass(); }
+                void setMass(dReal mass) { m_ode_object->setMass(mass); }
 
             protected:
                 void createManagedObject();
diff --git a/ag.cc b/ag.cc
index 70f9000..8b79c5d 100644
--- a/ag.cc
+++ b/ag.cc
@@ -158,6 +158,10 @@ namespace ag
         lua_setfield(L, -2, "setColor");
         lua_pushcfunction(L, object::setTexture);
         lua_setfield(L, -2, "setTexture");
+        lua_pushcfunction(L, object::setMass);
+        lua_setfield(L, -2, "setMass");
+        lua_pushcfunction(L, object::getMass);
+        lua_setfield(L, -2, "getMass");
     }
 
     static int loadModelSpecify(lua_State * L, bool static_data)
@@ -807,5 +811,35 @@ namespace ag
             }
             return 0;
         }
+
+        int getMass(lua_State * L)
+        {
+            int argc = lua_gettop(L);
+            if (argc == 1 && lua_istable(L, 1))
+            {
+                Engine::Object * obj = getObject(L, 1);
+                if (obj != NULL)
+                {
+                    lua_pushnumber(L, obj->getMass());
+                    return 1;
+                }
+            }
+            lua_pushnumber(L, 0);
+            return 1;
+        }
+
+        int setMass(lua_State * L)
+        {
+            int argc = lua_gettop(L);
+            if (argc == 2 && lua_istable(L, 1) && lua_isnumber(L, 2))
+            {
+                Engine::Object * obj = getObject(L, 1);
+                if (obj != NULL)
+                {
+                    obj->setMass(lua_tonumber(L, 2));
+                }
+            }
+            return 0;
+        }
     }
 }
diff --git a/ag.h b/ag.h
index ffb1207..5ad7f51 100644
--- a/ag.h
+++ b/ag.h
@@ -59,6 +59,8 @@ namespace ag
         int addRelTorque(lua_State * L);
         int setColor(lua_State * L);
         int setTexture(lua_State * L);
+        int getMass(lua_State * L);
+        int setMass(lua_State * L);
     }
 }
 
diff --git a/tests/bowling.lua b/tests/bowling.lua
index bda689d..16dc1ea 100644
--- a/tests/bowling.lua
+++ b/tests/bowling.lua
@@ -15,20 +15,21 @@ function init()
     local ground = ag.createPlane(0, 0, 1, 0)
     ground:setColor(0.8, 0.5, 0.0)
     ground:setPosition(0, 0, -10)
-    ag.setCamera(0, -25, 10, 0, 0, 1, 0, 0, 1)
+    ag.setCamera(0.3, -25, 10, 0, 0, 1, 0, 0, 1)
     camx, camy, camz, cx, cy, cz = ag.getCamera()
 
     ball = ag.loadModel("checkerball", 0.5)
+    ball:setPosition(2*camx - cx, 2*camy - cy, 2*camz - cz)
+    ball:setMass(5)
     --ball = ag.createSphere(0.4)
     --ball:setColor(0.2, 0.2, 0.9)
-    ball:setPosition(2*camx - cx, 2*camy - cy, 2*camz - cz)
 end
 
 function mousebutton_down_event(button)
     local function button1()
         local newball = ball:clone()
         newball:setPosition(camx, camy, 1)
-        force = 800
+        force = 4000
         newball:addForce(force * (cx-camx),
                          force * (cy-camy),
                          force * (cz-camz))