lib/driving_physics/disk.rb in driving_physics-0.0.2.1 vs lib/driving_physics/disk.rb in driving_physics-0.0.3.1

@@ -78,35 +78,10 @@
     # convert acc/vel/pos to alpha/omega/theta
     def self.rotational(tangential, radius)
       tangential.to_f / radius
     end
 
-    # vectors only
-    def self.torque_vector(force, radius)
-      if !force.is_a?(Vector) or force.size != 2
-        raise(ArgumentError, "force must be a 2D vector")
-      end
-      if !radius.is_a?(Vector) or radius.size != 2
-        raise(ArgumentError, "radius must be a 2D vector")
-      end
-      force = Vector[force[0], force[1], 0]
-      radius = Vector[radius[0], radius[1], 0]
-      force.cross(radius)
-    end
-
-    # vectors only
-    def self.force_vector(torque, radius)
-      if !torque.is_a?(Vector) or torque.size != 3
-        raise(ArgumentError, "torque must be a 3D vector")
-      end
-      if !radius.is_a?(Vector) or radius.size != 2
-        raise(ArgumentError, "radius must be a 2D vector")
-      end
-      radius = Vector[radius[0], radius[1], 0]
-      radius.cross(torque) / radius.dot(radius)
-    end
-
     attr_reader :env
     attr_accessor :radius, :width, :density, :base_friction, :omega_friction
 
     def initialize(env)
       @env = env
@@ -126,9 +101,14 @@
     end
 
     def normal_force
       @normal_force ||= self.mass * @env.g
       @normal_force
+    end
+
+    # E = (1/2) (I) (omega^2)
+    def energy(omega)
+      0.5 * self.rotational_inertia * omega ** 2
     end
 
     def alpha(torque, omega: 0, normal_force: nil)
       (torque - self.rotating_friction(omega, normal_force: normal_force)) /
         self.rotational_inertia