diff --git a/DIRECTORY.md b/DIRECTORY.md
index c781b17bf..588d0b1e5 100644
--- a/DIRECTORY.md
+++ b/DIRECTORY.md
@@ -715,6 +715,7 @@
   * [Archimedes Principle](physics/archimedes_principle.py)
   * [Casimir Effect](physics/casimir_effect.py)
   * [Centripetal Force](physics/centripetal_force.py)
+  * [Grahams Law](physics/grahams_law.py)
   * [Horizontal Projectile Motion](physics/horizontal_projectile_motion.py)
   * [Hubble Parameter](physics/hubble_parameter.py)
   * [Ideal Gas Law](physics/ideal_gas_law.py)