Domain: Natural Science — Physics
Target concept: Inertia and Mass

Video generation prompt: Two identical inclined tracks are placed side by side on a table. A 100 g wooden sphere is released from the left track, while a 500 g metallic sphere of the same shape is released from the same height on the right track.

Evaluation guide:
(i) Target concept: Rolling acceleration down an incline is independent of mass. For a wooden sphere and a metallic sphere of the same solid spherical shape, the gravity component driving them along the incline (m·g·sinθ) and the combined translational-plus-rotational inertia they must overcome both scale with mass m, so mass cancels out of Newton's second law: a = (5/7)·g·sinθ for a uniform solid sphere, the same value for both spheres regardless of the 5x mass difference between them.
Minimum mechanism: both spheres roll without slipping (no sliding); air resistance is negligible; the two tracks are rigid, identical in length and incline angle, and parallel; both spheres are solid and share the same spherical shape; both are released from rest at the same height at the same instant; gravity is uniform; no other force (differing friction, wind, a hand nudging a sphere) intervenes.
(ii) Storyline: Frame 1: Static wide shot: two parallel inclined tracks on a table, the wooden sphere at rest at the top of the left track, the metallic sphere at rest at the top of the right track. Frames 2-8: Both spheres are released at the same instant and roll down continuously, staying side by side at every comparable point of the descent; neither one pulls ahead of the other. Frames 9-10: Both spheres reach the bottom of their tracks at essentially the same moment and come to rest at corresponding positions. Perspective: fixed frontal view, eye-level or slightly elevated, both full tracks and both spheres always in frame, no occlusion, consistent lighting throughout.

Manual:
Experimental Procedure
1. Place two identical straight inclined tracks side-by-side on a level table.
2. Place a 100 g wooden sphere at the top end of the left track.
3. Place a 500 g metallic sphere of identical spherical shape at the top end of the right track.
4. Release both spheres simultaneously from rest.
Observation of Experimental Phenomena
Despite the 5x mass difference, the wooden sphere and the metallic sphere accelerate down their tracks at the same rate and reach the bottom of their respective tracks at essentially the same time — neither sphere shows a sustained speed advantage during descent.
Summary of Experimental Principles
For a sphere rolling without slipping down an incline, the driving force is the gravity component along the track, F = m·g·sinθ, which is directly proportional to mass, and the translational-plus-rotational inertia the sphere must overcome is also proportional to mass. These two mass-dependencies cancel in a = F_net/m, so the rolling acceleration of a uniform solid sphere (a = (5/7)·g·sinθ) depends only on the incline angle and the sphere's shape, not on its mass. Because the wooden and metallic spheres share the same solid spherical shape, they accelerate identically and arrive together, illustrating that inertia and the gravitational driving force scale together with mass rather than one outweighing the other.

Prompt Grounding rubric:
level_1: No inclined tracks are visible; or only one inclined track is shown; or no spheres are present; or the spheres are not resting on the tracks; or the wooden sphere and the metallic sphere are not released from the same starting height; or the two tracks are not arranged side by side on a table.
level_2: Two inclined tracks sit side by side on a table, but at least one setup detail is wrong or missing: the wooden sphere is not at the top of the left track, the metallic sphere is not at the top of the right track, one sphere is not resting exactly at the top of its track before release, or the two spheres are not visibly the same shape and size (e.g., one looks cube-shaped or is clearly a different diameter).
level_3: Two inclined tracks of matching length and incline angle sit side by side on a table; a wooden sphere rests at the top of the left track and a metallic sphere rests at the top of the right track; both spheres are the same size and shape and are visibly stationary immediately before release; both begin moving at essentially the same moment from the same starting height.
level_4: Everything at the 3-point level holds, plus: both spheres stay fully visible within the frame for the whole video; the wooden sphere keeps a matte, light-toned wood-grain look and the metallic sphere keeps a smooth, reflective gray/silver look throughout; nothing (hands, tools, other objects) blocks either sphere or track; the camera viewpoint stays fixed and frontal for the entire video.
level_5: Everything at the 4-point level holds, plus: both spheres show no pre-roll or wobble before release and start moving at the same visible instant; the wooden-versus-metallic material contrast and the side-by-side framing of the two tracks stay unambiguous from first frame to last; the camera never pans, zooms, tilts, or repositions at any point.

Scientific and Causal Correctness rubric:
level_1: Only one sphere moves while the other stays motionless on its track; or neither sphere ever descends; or a sphere moves in a way unrelated to gravity (e.g., sliding sideways off the track, hovering, or rolling back up the incline).
level_2: Both spheres descend, but one sphere (wooden or metallic) shows an obvious, sustained lead over the other for most of the descent (clearly and consistently ahead by more than about one sphere-diameter across several comparable stages), implying that rolling acceleration depends on mass; or the lead between the two spheres flips back and forth repeatedly in a way that looks arbitrary rather than physically driven.
level_3: Both the wooden sphere and the metallic sphere begin from rest and descend continuously under gravity, with no floating or lifting; the two spheres reach the bottom of their tracks at approximately the same time, with neither one visibly leading by more than about one sphere-diameter at the moment either one arrives.
level_4: Everything at the 3-point level holds, plus: throughout the entire descent, not only at the finish, the wooden sphere and the metallic sphere stay side by side at every comparable stage (e.g., when one is at the halfway mark of its track, the other is close to the halfway mark of its own track too); no hidden push, magnet, or hand influences either sphere; both spheres visibly roll, rotating in step with their forward motion, rather than sliding without rotating.
level_5: Everything at the 4-point level holds, plus: at every comparable instant of the descent the two spheres remain visually side by side along their tracks, with no measurable, sustained gap ever opening between them despite the 5x mass difference; both spheres cross the bottom of their tracks within a fraction of a second of each other, clearly showing that rolling acceleration here does not depend on which sphere is five times heavier.

Spatiotemporal Consistency rubric:
level_1: A track or a sphere vanishes and reappears; a track suddenly changes its incline angle or position mid-video; a sphere instantly relocates from one point on its track to another without visibly rolling through the space in between; the tabletop's texture or color changes abruptly between frames; the overall scene lighting jumps from one look to a completely different one with no transition; a sphere changes shape (e.g., flattens or stretches) during motion.
level_2: A sphere skips from near the top of its track to the middle with no visible rolling in between; one track's visible length changes between the start and the end of the video; a sphere's shadow jumps to a position inconsistent with where the light is coming from; a sphere's rotation starts, stops, and restarts in a way that doesn't match its forward motion; the camera's framing shifts sideways or up/down partway through the video.
level_3: Neither sphere disappears, teleports, or changes shape; each sphere moves along its track as a continuous rolling path with no visible gap or skip; each sphere's shadow stays attached beneath it and points in the same direction throughout, consistent with a single fixed light source; both inclined tracks stay rigid and unchanged in shape and position; the tabletop stays visually stable; neither sphere's motion suddenly jumps or freezes.
level_4: Everything at the 3-point level holds, plus: each sphere's path stays confined to the surface of its own track: no sphere drifts sideways off the track, lifts off it, or bounces away from it; each sphere's rotation looks smooth and matches its rolling motion, with no sudden freezing or reversal of spin; each shadow's size and softness change naturally as its sphere moves from the top (smaller, sharper shadow) toward the bottom (larger, softer shadow); neither track's edges warp or jitter.
level_5: Everything at the 4-point level holds, plus: each sphere's motion down its own track looks continuously smooth, with no sudden speed jump or freeze at any point; each sphere's path stays a single smooth line along its incline with no kinks or sideways drift; each shadow continuously follows its own sphere without ever lagging behind, detaching, or jumping to a different spot; neither track ever appears bent, stretched, or otherwise distorted in a way that breaks their side-by-side parallel alignment.