On a clean, flat, smooth surface (polished concrete is good) place a quarter. Position the flat front edge of either fork over the coin (center) lower fork until it's resting on the surface of the coin. Back the lift slowly - as the fork pulls off the coin, it will flip upwards and land on the fork.
The reason it works is that quarters have a raised edge around the circumference. When the fork pulls off that edge correctly, it catches the rim a little, tilts the coin upward effectively SNAPPING the quarter with enough force (weight of the fork) to flip up in a backward arc to land on the fork.
I am told some poisonous snakes use a similar principle to attack in the 180-degree opposite direction they are moving.
That's apparently one reason some people ignorant enough to chase a rattlesnake (or other pit viper) that's slithering away from them, get bitten/killed. The snake can use curled spring-power to reverse their momentum and propel their head (fangs) forward to strike at lightning speed.