Domain: Humanities and Social Sciences — Linguistics
Target concept: Tuning forks of different pitches vibrating in water produce visibly different spray patterns — a finer, denser mist for the higher-pitched (smaller) fork versus a coarser, sparser spray of larger droplets for the lower-pitched (larger) fork — since individual vibration cycles are too fast to see as discrete splashes.

Video generation prompt: On the table, place two metal tuning forks of different sizes above a shallow, transparent trough of still water. Strike the first fork with a mallet and lower its prongs into the water; once that fork is vibrating in the water, strike the second fork with the same mallet motion and lower its prongs into the water at the same depth, so both forks' effects on the water are visible together.

Evaluation guide:
(i) Target concept: Tuning-fork vibration frequency shapes the water spray thrown off by the immersed prongs: the smaller, higher-pitched fork vibrates faster and produces a finer, denser spray of smaller droplets, while the larger, lower-pitched fork vibrates slower and produces a coarser, sparser spray of larger droplets.
Minimum mechanism: The immersed vibrating prongs must transfer their oscillation into the water as a continuous fine spray rather than as isolated, individually countable splashes; real tuning forks vibrate far too fast for the eye or a standard video frame rate to resolve as separate timed events; the two forks' sprays must differ visibly in droplet size and density because of their size difference, under the same strike and immersion conditions.
(ii) Storyline: [Frame 0–2] Two differently sized tuning forks rest side-by-side above the trough; mallet held near the first fork. [Frame 3–4] Mallet strikes the first fork: visible contact and prong recoil. [Frame 5–6] First fork's prongs enter the water: clean surface break, no splash from the entry itself. [Frame 7–9] A continuous fine spray builds up at the first fork's prong tips and stays visible while that fork keeps vibrating. [Frame 8–9] Mallet strikes the second fork with the same motion. [Frame 10] Second fork's prongs enter the water at the same depth. [Frame 10–10+] A continuous spray also builds up at the second fork's prong tips, visibly different from the first fork's spray in droplet size, density, or spread, with both sprays visible at once for direct comparison; viewpoint stays fixed, frontal, eye-level, keeping both forks and the trough fully in frame throughout.

Manual:
Experimental Procedure
1. Place two metal tuning forks of different sizes side-by-side on a table, directly above a shallow, transparent water-filled trough.
2. Strike the first fork once with the mallet and lower its prongs into the water to the marked depth.
3. While the first fork is still vibrating in the water, strike the second fork with the same mallet motion and lower its prongs into the water to the same depth.
Observation of Experimental Phenomena
A fine spray of water droplets forms at the surface where each fork's prongs vibrate; the smaller fork produces a denser, finer spray of smaller droplets, while the larger fork produces a sparser spray of larger, more scattered droplets.
Summary of Experimental Principles
Tuning forks of different sizes vibrate at different natural frequencies; the smaller fork's higher-frequency vibration agitates the water surface more rapidly, atomizing it into a finer, denser spray, while the larger fork's lower-frequency vibration produces a coarser, sparser spray with larger droplets.

Prompt Grounding rubric:
level_1: The scene does not show two metal tuning forks of visibly different sizes together above a trough; no shallow transparent trough is present; no mallet is shown; neither fork's prongs are ever lowered into water.
level_2: A trough and at least one tuning fork are visible, but the second fork never appears together with the first above the trough, or the mallet never makes contact with either fork, or a fork's prongs are held above the water without ever being lowered in, or the two forks look the same size instead of visibly different.
level_3: Two metal tuning forks of visibly different sizes stand side-by-side above a shallow transparent trough of water on the table; a mallet strikes at least one fork; both forks' prongs are lowered into the water at some point in the clip; each fork's prongs break the water's surface cleanly, without a splash from the entry motion itself, matching the objects and setup described in the prompt.
level_4: All elements of 3-score are present, and the mallet strikes the first fork, that fork's prongs enter the water, and only afterward does the mallet strike the second fork and lower its prongs in at the same depth; the two strikes are never simultaneous and never in reverse order; both forks stay planted in the same spot on the table except for the intended striking and immersing motion.
level_5: All elements of 4-score are present, and the mallet's strike on the second fork follows the same swing trajectory, angle, and contact point as its strike on the first fork; both forks' prongs reach the same immersion depth in the water, judged by eye against the trough's waterline; neither fork, the mallet, nor the trough ever shifts position or leaves the frame except for the deliberate striking and immersing actions shown.

Scientific and Causal Correctness rubric:
level_1: No spray or droplet disturbance appears at either fork's prong tips after striking; both forks look identical in their effect on the water (either both produce spray or neither does); or the visible spray appears at the second, later-struck fork before the first fork's prongs even reach the water.
level_2: Only one fork's prongs produce a visible spray while the other's produce none at all, even though both are struck and immersed the same way; or the spray from each fork looks visually indistinguishable in droplet size and density, giving no basis to tell the forks apart by their water effect.
level_3: Once each fork's prongs enter the water, a fine spray of droplets forms right at that fork's prong tips (not elsewhere in the trough); the spray at the two forks looks visibly different from each other in droplet size or density (e.g., one spray reads as finer and mistier, the other as coarser and more scattered); no spray appears before its fork is struck and immersed.
level_4: All elements of 3-score are present, and specifically the smaller fork's spray is the finer, denser one (small droplets, tight mist-like spread) while the larger fork's spray is the coarser, sparser one (larger droplets, wider scattered spread), not the reverse; each spray persists continuously while its fork is still visibly vibrating and settles down as the vibration visibly damps out.
level_5: All elements of 4-score are present, and the size/density contrast between the two sprays is unambiguous and holds for as long as both sprays are visible on screen (the smaller fork's mist never coarsens to match the larger fork's droplets or vice versa); neither spray is masked or exaggerated by unrelated water disturbance (e.g., overflow, sloshing from the trough being bumped, or ripples unrelated to either fork's vibration).

Spatiotemporal Consistency rubric:
level_1: A tuning fork, the mallet, or the trough appears in a completely different position from one frame to the next with no motion shown connecting the two (e.g., a fork is upright above the trough in one frame and already submerged in the next); the water surface in the trough vanishes, reappears, or changes level with no fork entering or leaving it to explain the change; the lighting abruptly flips (e.g., bright to dark or vice versa) with no visible cause; the trough or a fork visibly warps, stretches, or distorts in shape; or the camera viewpoint jumps or rotates instead of staying fixed.
level_2: A fork's motion from being struck to entering the water skips visible steps (e.g., the prong tips jump from mid-air straight to producing spray with no entry moment shown); the trough or a fork drifts to a different spot on the table partway through the clip; the mallet's contact with a fork produces no visible recoil or reaction from that fork; or the background behind the forks and trough shifts in color, texture, or scale between frames.
level_3: Both forks and the trough stay in the same spot on the table for the whole clip; the mallet moves in one continuous path from raised, to striking contact, to pulling away, for each fork in turn; the water surface in the trough stays flat and undisturbed except directly where a fork's prongs are immersed or spraying; neither fork bends, stretches, or passes through the trough or table.
level_4: All elements of 3-score are present, and the mallet's swing toward each fork follows a smooth arc rather than jumping partway through its motion; each fork's prongs vibrate with a small, in-place back-and-forth motion (not a large sideways whipping or drifting motion); the boundary between trough, water, and table stays sharply defined rather than blurring or fusing together as objects move.
level_5: All elements of 4-score are present, and the mallet never appears to pass through a fork or the trough at any point in its swing; the two sprays stay visually anchored to their own fork's prong tips throughout (never drifting toward the other fork or merging into a single shared spray); once each spray subsides, the water surface settles back to the same flat, undisturbed level it had before that fork was struck.