diff --git a/ball.hpp b/ball.hpp
index 5388f9d..ae58873 100644
--- a/ball.hpp
+++ b/ball.hpp
@@ -13,7 +13,7 @@ protected:
     /**
      * Calcule les forces appliquées à l'objet
      */
-    sf::Vector2f getForces(State state);
+    virtual sf::Vector2f getForces(State state);
 
     static constexpr float ATTRACTION = 10;
     static constexpr float MOVE = 10;
diff --git a/physics_object.hpp b/physics_object.hpp
index 4ec6ae5..0c3b961 100644
--- a/physics_object.hpp
+++ b/physics_object.hpp
@@ -14,7 +14,7 @@ protected:
     /**
      * Calcule les forces appliquées à l'objet
      */
-    sf::Vector2f getForces(State state);
+    virtual sf::Vector2f getForces(State state);
 
     static constexpr float GRAVITY = 10;