Domain: Engineering — Agricultural Engineering
Target concept: Immerse the wet corn stalks in clean water, and confirm that most of the stalks sink to the bottom, with only a small portion at the top remaining above the water surface.

Video generation prompt: Prepare a transparent container filled with clean water. Take a moist corn stalk and gently place it into the water. Release it naturally without pressing. During the placement process, keep the camera focused on the contact and interaction between the stalk and the water.

Evaluation guide:
(i) Target concept: Density-driven sinking of a water-saturated corn stalk, where the stalk's length relative to the container's water depth (not a buoyant floating equilibrium) determines how much of it stays above the surface.
Minimum mechanism: The corn stalk must be thoroughly saturated with water (pith and vascular tissue fully wetted, no trapped air pockets), which raises its bulk density to slightly above that of clean water (roughly 1.0–1.05 g/cm³ versus water's 1.0 g/cm³); a dry stalk would float instead, buoyed by air trapped in its pith. Because its density now exceeds water's, the stalk sinks and comes to rest on the container's bottom rather than reaching a floating equilibrium. The small dry segment that remains above the waterline is a geometric consequence of the stalk being longer than the water is deep, not evidence of buoyant support.
(ii)Storyline: [Phase 1: Setup] Transparent container filled with still, clear water occupies central frame; ambient lighting reveals water clarity and container transparency. [Phase 2: Introduction] Moist corn stalk enters frame vertically, held by hand above surface; stalk surface shows dampness (sheen, no dust). [Phase 3: Contact] Stalk tip touches water surface; meniscus deforms visibly; no splash or rebound. [Phase 4: Descent] Stalk sinks continuously and steadily; water parting smoothly along length; upper portion remains emergent. [Phase 5: Resting state] Final static state: stalk vertical or near-vertical, its lower end resting on the container bottom, most of its length submerged; a short top segment stays dry and above the surface because the stalk is longer than the water is deep; water surface calm and level around the stalk; no floating, no external support, no distortion. Perspective: Fixed frontal/slightly angled view ensuring full stalk and waterline are simultaneously visible; no occlusion; depth cues preserved via container edges and water refraction.

Manual:
Experimental Procedure
1. Fill a transparent container with clean water until ~¾ full.
2. Take one moist corn stalk and hold it vertically above water surface.
3. Gently lower and release it onto water surface—no pushing or tilting.
Observation of Experimental Phenomena
Most of the stalk sinks below water surface; only a small portion (e.g., top 1–2 nodes) remains visibly above surface.
Summary of Experimental Principles
Once thoroughly wetted, a corn stalk's tissue (fibrous cellulose plus water-filled pore space) reaches a bulk density slightly above that of clean water; unlike a dry stalk, which floats on trapped air in its pith, the saturated stalk sinks and settles on the container's bottom. The small segment that stays above the waterline is not a buoyant float — it remains dry simply because the stalk's length exceeds the depth of the water in the container.

Prompt Grounding rubric:
level_1: No transparent container of water appears; no corn stalk is shown; the stalk is not placed into water by hand; the camera never shows the stalk touching or entering the water.
level_2: A container holds liquid, but the liquid is not clearly clean water (murky, colored, or foam-covered) or the container is not transparent; the corn stalk shown is visibly dry (no wet sheen); the stalk-to-water contact point is off-frame or blocked.
level_3: A transparent container of clear water and a visibly wet corn stalk (glistening surface, no dust) are both shown; a hand lowers the stalk toward the water and releases it, with a visible moment of hand-stalk separation; the camera frame includes the stalk tip touching the water surface.
level_4: Everything in score 3 holds, and in addition: the stalk stays fully inside the frame through its entire descent; the hand is completely out of frame before the stalk begins sinking; nothing else in the shot blocks the view of the stalk entering the water; the container itself never shifts position or tips.
level_5: Everything in score 4 holds, and in addition: the stalk enters the water pointing straight down or nearly so, without being thrown sideways or spun; the water surface is calm just before and during entry; the placement-to-settling sequence plays as one continuous shot with no cuts, glitches, or duplicated frames.

Scientific and Causal Correctness rubric:
level_1: The corn stalk floats with almost none of it below the surface, or it dissolves/falls apart in the water, or it hangs suspended mid-depth without ever settling against the container bottom; none of these match how a water-saturated stalk behaves.
level_2: The stalk sinks only partway, with most of its length still above the surface, or it sinks completely with no segment left above the waterline, or it bobs/oscillates up and down after entering the water instead of settling.
level_3: Most of the stalk's length ends up submerged toward the container bottom, while a distinctly smaller segment near the top stays above the waterline; the stalk's shape, color, and rigidity are unchanged by the water (no swelling, softening, or color bleed).
level_4: Everything in score 3 holds, and in addition: the dry segment that stays above the surface is specifically the top end of the stalk (not a middle or base section); the stalk keeps a straight, rigid form throughout; the water around it stays clear and undisturbed except for the brief displacement at the moment of entry.
level_5: Everything in score 4 holds, and in addition: the submerged and emergent portions of the stalk line up as one unbroken piece (no visible gap, kink, or misalignment at the waterline); no clinging air bubbles are visible on the submerged surface; the water surface curves naturally against the stalk rather than staying flat; nothing in the shot (string, clamp, or visible support) explains the stalk's position other than it resting on the container bottom with its top segment protruding because the stalk is longer than the water is deep.

Spatiotemporal Consistency rubric:
level_1: The container's size, shape, or position changes abruptly between shots; the stalk appears or disappears without the placement action shown; the water surface breaks apart or flickers; the light source or shadow direction changes abruptly partway through; the camera cuts or spins with no continuous motion connecting the views.
level_2: The stalk's position jumps by more than its own length between consecutive moments without a visible transition; the container shakes or tips sharply; ripples appear on the water surface all at once instead of spreading outward from where the stalk entered; the hand releases the stalk while it is still in the air, and the next moment shows it already underwater with the descent itself skipped.
level_3: The container stays in the same place and the same size throughout; the water surface stays level and unbroken; the hand is fully clear of the stalk before the stalk touches the water; there is no moment where the stalk's shape blurs, tears, or merges with the container or water.
level_4: Everything in score 3 holds, and in addition: the stalk's descent through the water is a single smooth, continuous motion with no stutter, freeze, or skipped frames; the ripple pattern from the stalk's entry spreads outward from the entry point rather than appearing all at once; the container's edge and the water's surface stay crisp and clearly defined in every shot.
level_5: Everything in score 4 holds, and in addition: the sequence of events is unambiguous and in this order: hand holds the stalk above the water, the stalk's tip touches the surface, the water visibly parts at that contact point, the stalk descends, and the stalk comes to rest with most of it submerged and a short top segment above the surface; nothing in the sequence repeats, reverses, or skips a step.