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

Video generation prompt: A balance scale is placed on the table, with a cubic iron block placed on the left pan and a gold block of the same shape and volume placed on the right pan.

Evaluation guide:
(i) Target concept: Density determines mass for fixed volume; unequal mass causes torque imbalance on a lever system (balance scale).
Minimum mechanism: Two solid, non-porous, macroscopic cubic blocks of identical geometric dimensions but different elemental composition (Fe vs Au); gravitational field uniform; scale pivots freely with negligible friction; no external forces (wind, vibration, contact) act during observation.
(ii)Storyline: Frame 1–3: Stable wide shot showing empty balance scale centered on table. Frame 4–6: Iron cube placed onto left pan; remains still. Frame 7–9: Gold cube placed onto right pan; remains still. Frame 10–end: Beam rotates smoothly around fulcrum; right pan lowers continuously and settles in lowered position; left pan rises correspondingly; both cubes stay fixed on pans with no sliding or rebound; entire sequence viewed from fixed frontal angle with full scale and both pans continuously visible and unoccluded.

Manual:
Experimental Procedure
1. Place a balance scale flat on a stable table.
2. Place a cubic iron block on the left pan.
3. Place a cubic gold block of identical shape and volume on the right pan.
Observation of Experimental Phenomena
The right pan (gold side) descends while the left pan (iron side) rises; the beam tilts downward on the right.
Summary of Experimental Principles
Gold has higher density than iron; therefore, for equal volumes, the gold block has greater mass and exerts greater gravitational force on its pan, causing the scale to tip toward the gold side.

Prompt Grounding rubric:
level_1: No balance scale visible; or no cubic iron block present; or no cubic gold block present; or the iron and gold blocks are not placed on opposite pans; or either block is entirely absent from the scene; or a block's shape is non-cubic (e.g., sphere, cylinder, irregular lump); or the scale and both blocks are never simultaneously visible in the same frame.
level_2: The balance scale is present and centered, but only one block (iron or gold) is placed while the other pan is empty; or both blocks are present but at least one is non-cubic; or both blocks are placed on the same pan; or the two blocks are stacked on top of each other or otherwise not each resting in its own separate pan.
level_3: The balance scale is present with a cubic block on the left pan and a cubic block on the right pan; the two cubes are visibly distinct in material appearance (e.g., differing metallic luster or hue); no other objects interfere with the view; the scale, both cubes, and their left/right pan assignment are all present together in a single continuous scene.
level_4: All elements from score 3 are present AND the left cube is identifiable as iron (gray-silvery metallic color, matte or slightly oxidized surface) AND the right cube is identifiable as gold (yellow-gold metallic color, warm luster); the two cubes are the same apparent size and shape; no extraneous objects, occlusions, or misplacements are visible; the camera viewpoint stays fixed and frontal throughout.
level_5: All elements from score 4 are present AND both cubes sit flush and level on their respective pans throughout, with no sideways tilt, sinking into the pan, or floating above it; the beam starts perfectly level before any tilting motion begins; no visual artifacts, cuts, or discontinuities appear at any point; the cubes' materials, colors, sizes, positions, and the camera framing match the posted prompt exactly and continuously from start to end.

Scientific and Causal Correctness rubric:
level_1: No directional imbalance is shown at all: the beam stays level throughout even though both cubes are present, so no tilt is depicted; or the iron and gold cubes look visually identical in color/luster so no material difference can be judged; or neither pan visibly moves after both cubes are placed, leaving the mass-density outcome undemonstrated.
level_2: The beam does tilt, but the direction contradicts the density relationship: the left (iron) pan ends up lower than the right (gold) pan; or the tilt begins before both cubes are fully placed on their pans; or the tilt direction reverses partway through the sequence; or a pan visibly descends before both cubes are simultaneously resting on the scale.
level_3: The right pan (holding the gold cube) is lower than the left pan (holding the iron cube); the beam tilts downward on the right side; both cubes stay stationary on their pans while this happens; no pan motion contradicts the expected static outcome; the color difference between the iron cube (gray-silvery) and the gold cube (yellow-gold) is visually apparent.
level_4: All elements from score 3 are present AND the rightward tilt is sustained rather than momentary or flickering; nothing suggests the two cubes have equal mass (e.g., no return to level, no equal counter-tilt); no misleading cue implies equal density (e.g., matching surface reflectivity, a label, or on-screen text implying equivalence); the sequence clearly shows: iron and gold cubes placed on opposite pans, then the beam tilts and settles with the gold (right) pan lower.
level_5: All elements from score 4 are present AND the final tilt is unambiguous and stable, with the right (gold) pan clearly and lastingly lower and no doubt about which side is heavier; nothing in the shot competes with this reading (no shadow suggesting a pan is being lifted, no visible wire or support, no pan bending out of shape); the tilt does not begin before placement or continue after either cube would be removed; the link between the cubes' materials and the observed tilt direction is fully readable from the visuals alone.

Spatiotemporal Consistency rubric:
level_1: The balance scale itself vanishes from the frame or reappears in a different position/orientation between consecutive frames; or the iron cube or gold cube instantly appears already resting on its pan with no visible placement motion, or jumps to a new spot on the pan with no motion in between; or a pan's position or orientation changes abruptly rather than continuously; or the overall lighting flips abruptly between adjacent frames (e.g., a bright frame directly followed by a dark one); or the beam visibly fractures, bends at a point other than the fulcrum, or rotates about an axis other than the central pivot.
level_2: The scale, pans, and cubes stay roughly in place but show pronounced jitter, warping, or shape-morphing frame to frame; or a pan's surface flickers in and out of view; or the shadow cast by the iron cube falls on the opposite side from the shadow cast by the gold cube even though both should be lit by the same source (e.g., the iron cube's shadow falls left while the gold cube's falls right); or the camera view rotates or zooms with a visible jump instead of a smooth pan or zoom.
level_3: The scale, both pans, and both cubes stay continuously visible and spatially coherent, with none of them vanishing, jumping to a new position, or morphing into a different shape between frames; the shadow under the iron cube and the shadow under the gold cube each stay on the same side of their respective cube for the whole sequence, consistent with one unmoving light source, and never swap sides or disappear as the beam tilts; the beam's rotation is one smooth, continuous sweep rather than a sudden snap to its final angle; there are no visible cuts or scene transitions.
level_4: All elements from score 3 are present AND the beam's tilt is physically plausible: it rotates smoothly about the central fulcrum without drifting sideways; neither cube slides, bounces, or shifts position on its pan while the beam moves; neither cube sinks into or pokes through the pan beneath it; the edges of both cubes and the outline of each pan keep a consistent, well-defined shape throughout the motion.
level_5: All elements from score 4 are present AND the beam's rotation proceeds at a smoothly varying speed with no visible jump, stutter, or repeated frame; the beam, pans, and cubes show no visible shaking or vibration at any point; the edges of the cubes and the rims of the pans stay crisp and stable rather than flickering or shimmering; the cubes and pans in the foreground move consistently with the table and scale base behind them, with no visible sliding mismatch between the two; the whole sequence is free of any visible break in space or time.