Some physical laws, explained ten times in words, are not as valuable as witnessing a perfect demonstration firsthand. The essence of Newton's First Law (the law of inertia) lies in "maintaining a state." And the most exciting verification is demonstrating how an object, while being forced to change direction, stubbornly maintains its state in another direction. Our exhibit constructs this thought experiment into a highly dramatic scene: a train moving at a constant speed in a straight line (representing an ideal "force-free" horizontal environment), an arched bridge (providing the trigger point for the external force changing the vertical motion of a ball), and a sudden vertical launch (giving the ball a new vertical state). After the ball is launched, its fate is entirely composed of two independent motions: a uniformly decelerated ascent and descent in the vertical direction, and a horizontal, uniform motion maintained by inertia, perfectly mirroring the train's motion. The trajecto
