Final answer:
Football helmets in the 1920s utilized the principle of inertia to protect players' heads from sudden changes in motion during impacts and collisions.
Step-by-step explanation:
Inertia is the tendency of an object to resist changes in its motion. In the context of football helmets in the 1920s, inertia applied to how the helmets protected the players' heads from sudden changes in motion during collisions or impacts.
When a player wearing a football helmet gets hit, the helmet's design and padding help to absorb some of the force exerted on the head. This reduces the acceleration and changes in motion that the head experiences, limiting the risk of head injuries like concussions.
By utilizing padding and sturdy construction, the helmets in the 1920s provided a layer of protection by harnessing the principle of inertia to keep the players' heads more stable and less affected by the external forces of the game.