diff --git a/physics/horizontal_projectile_motion.py b/physics/horizontal_projectile_motion.py
index 0f27b0617..a747acd72 100644
--- a/physics/horizontal_projectile_motion.py
+++ b/physics/horizontal_projectile_motion.py
@@ -17,7 +17,7 @@ For more info: https://en.wikipedia.org/wiki/Projectile_motion
 from math import radians as angle_to_radians
 from math import sin
 
-# Acceleration Constant on hearth (unit m/s^2)
+# Acceleration Constant on Earth (unit m/s^2)
 g = 9.80665