The Free Body Diagram Newton's 2nd Law says that for an object F= ma Key phrase here is for an object. So before we can apply F= ma to any given object we isolate the forces acting on this object Physics 121: Lecture 8, Pg 7Physics 121: Lecture 8, Pg 7 The Free Body Diagram Newton’s 2nd Law says that for an object F = ma. Key phrase here is for an object. So before we can apply F = ma to any given object we isolate the forces acting on this object: