diff --git a/include/Kyoto/Math/CQuaternion.hpp b/include/Kyoto/Math/CQuaternion.hpp
index 87ebb18b..83a335c3 100644
--- a/include/Kyoto/Math/CQuaternion.hpp
+++ b/include/Kyoto/Math/CQuaternion.hpp
@@ -71,6 +71,9 @@ public:
   float GetX() const { return x; }
   float GetY() const { return y; }
   float GetZ() const { return z; }
+  const CVector3f& GetImaginary() const { 
+    // TODO: hack! has a Vector3f field?
+    return *reinterpret_cast<const CVector3f*>(&x); }
 
 private:
   float w;
diff --git a/include/MetroidPrime/CPhysicsActor.hpp b/include/MetroidPrime/CPhysicsActor.hpp
index 5490f5eb..65217796 100644
--- a/include/MetroidPrime/CPhysicsActor.hpp
+++ b/include/MetroidPrime/CPhysicsActor.hpp
@@ -141,7 +141,7 @@ public:
   void MoveToWR(const CVector3f&, float);
   void MoveToInOneFrameWR(const CVector3f&, float);
   CVector3f GetMoveToORImpulseWR(const CVector3f& impulse, float d) const;
-  CAxisAngle GetRotateToORAngularMomentumWR(const CQuaternion& q, float d) const;
+  CVector3f GetRotateToORAngularMomentumWR(const CQuaternion& q, float d) const;
   void RotateToWR(const CQuaternion&, float);
 
   void MoveToOR(const CVector3f&, float);
diff --git a/libc/math.h b/libc/math.h
index 885a0815..e1f4d940 100644
--- a/libc/math.h
+++ b/libc/math.h
@@ -76,6 +76,7 @@ double atan2(double y, double x);
 _MATH_INLINE float sinf(float x) { return (float)sin((double)x); }
 _MATH_INLINE float cosf(float x) { return (float)cos((double)x); }
 float tanf(float x);
+double acos(double x);
 float acosf(float x);
 
 double ldexp(double x, int exp);
diff --git a/src/MetroidPrime/CPhysicsActor.cpp b/src/MetroidPrime/CPhysicsActor.cpp
index bcc243ac..a21b8d6a 100644
--- a/src/MetroidPrime/CPhysicsActor.cpp
+++ b/src/MetroidPrime/CPhysicsActor.cpp
@@ -229,7 +229,13 @@ CVector3f CPhysicsActor::GetMoveToORImpulseWR(const CVector3f& trans, float d) c
   return (GetMass() * impulse) * (1.f / d);
 }
 
-CAxisAngle CPhysicsActor::GetRotateToORAngularMomentumWR(const CQuaternion& q, float d) const {
-  // TODO
-  return CAxisAngle();
+CVector3f CPhysicsActor::GetRotateToORAngularMomentumWR(const CQuaternion& q, float d) const {
+  if (q.GetW() > 0.99999976f) {
+    return CVector3f::Zero();
+  } else {
+    const CVector3f rotated = GetTransform().Rotate(q.GetImaginary());
+    
+    float ac = acos(q.GetW());
+    return rotated.AsNormalized() * ((ac * 2.0f) * (1.0f / d)) * xf0_inertiaTensor;
+  }
 }