The forces of gravity
or, more accurately, inertia. When I was but ten, my partner Mike and I were running around playing with some old Master locks dad had brought home from Ford, discard lockout/tagout locks from obsolete machinery.
Now, when these were attached to their respective machies, they each included about 7′ of steel chain making them, well, more or less, theft resistant.
To a ten year old, discovering the forces of inertia by whirling a weight on the end of a string is one of the most amusing science lessons, and as I whirled, Mike walked around the corner of the house.
The lock hit him in the temple and laid him out like a mackerel.He flew off to the side and hit the ground perfectly horizontal, and just as he did, I noticed him for the first time, his mom walking out their front door, and my mom pulling in the drive.
Mom started hitting me with something, I think it was the back of her hand, or maybe it was a brick. Mike came to, sitting up and rubbing his temple, saying “I see stars”. His brother Bobbie yells “MICKEY GETS EVERYTHING!” and Mike’s mom, not to be outdone, starts wailing on Mike’s freshly throbbing headwound with a plunger handle.
How the hell did I survive childhood?

Applied physics
I cannot say that I exactly replicated the scene depicted in Og’s story
To a ten year old, discovering the forces of inertia by whirling a weight on the end of a string is one of the most amusing science lessons, and as I whirled, Mike walked a…
“Mike’s mom, not to be outdone, starts wailing on Mike’s freshly throbbing headwound”
Huh? do you have a clue as to why she did that? and what does Mike send his mother on Mother’s Day?
Mike’s mom didn’t want to feel left out. “I want a kid to hit!! Oh, here’s one!”
Congratulations on your independent invention of the dum-dum or sap….LOL