Here's why:
* Inertia: Inertia is the tendency of an object to resist changes in its state of motion. This means an object at rest wants to stay at rest, and an object in motion wants to stay in motion at a constant speed and direction.
* The Horse: The galloping horse is in motion.
* The Rider: The rider is also in motion, moving along with the horse.
* Sudden Stop: When the horse suddenly stops, the rider's body continues to move forward due to inertia.
* Result: This forward motion causes the rider to be thrown over the horse's head and land on the ground.
In essence, the rider's body continues to move forward because of inertia, even though the horse has stopped.