Domain: Natural Science — Physics
Target concept: Principle of communicating vessels

Video generation prompt: Place a U-tube manometer on the table, and inject an appropriate amount of water into the U-tube. After the system reaches equilibrium, observe the height of the liquid in both sides of the tube.

Evaluation guide:
(i) Target concept: Hydrostatic equilibrium in open, connected, homogeneous liquid columns under uniform gravity.
Minimum mechanism: Liquid must be incompressible, cohesive, and subject to uniform gravitational acceleration; tube must be open to atmosphere at both ends; no external pressure differentials or flow-driving forces may persist at observation time.
(ii)Storyline: [Frame 0–3] U-tube placed statically on tabletop → [Frame 4–6] Water injected simultaneously into both arms (visible inflow) → [Frame 7–10] Inflow stops; liquid oscillates briefly then becomes completely still → [Final frames] Two motionless, vertically aligned, equally high liquid columns with shared continuous fluid path through the U-bend; viewpoint remains fixed, front-facing, and orthogonal to tabletop plane; entire U-tube and both columns remain fully visible and unoccluded.

Manual:
Experimental Procedure
1. Place a transparent U-shaped glass tube upright on a flat horizontal tabletop.
2. Inject water into both arms of the U-tube until liquid fills the bottom bend and rises visibly in each arm.
3. Wait for liquid to settle and become motionless.
Observation of Experimental Phenomena
After settling, the water surface in the left arm and the water surface in the right arm are at exactly the same height and perfectly level.
Summary of Experimental Principles
This demonstrates the Principle of Communicating Vessels: when a homogeneous liquid is at rest in connected vessels open to the atmosphere, its free surface will settle at the same horizontal level in all arms.

Prompt Grounding rubric:
level_1: No U-shaped tube is visible; no water appears anywhere in the shot; no tabletop or supporting surface is shown; the two-armed liquid-column setup required for this demonstration is completely absent.
level_2: A U-shaped tube is visible but does not sit flat on a horizontal tabletop (e.g., it is tilted, propped at an angle, or held above the surface); water is present but confined to only one arm, or appears as a disconnected droplet rather than a continuous column; no two side-by-side liquid columns are established.
level_3: The U-tube rests on a visible horizontal tabletop; water fills both arms; two separate liquid columns are visible, one in each arm; the water is not shown actively being poured or in motion; it appears at rest at the moment of observation.
level_4: The tube sits on a visible horizontal tabletop with two stationary water columns, one per arm, each staying flush against its own tube wall with no bulging, overflow, or meniscus distortion that would break the column apart; the glass tube itself is intact, symmetric, and clearly U-shaped, with no cracks, gaps, or occlusion hiding either arm.
level_5: The tube and its two columns appear exactly as described above, and in addition the whole U-tube is centered in the frame, stays in sharp focus, and fills roughly 60% or more of the frame's vertical extent; no glare, clipping, or rendering artifact obscures either liquid column or the bend connecting them.

Scientific and Causal Correctness rubric:
level_1: The two water columns settle at clearly unequal heights (one surface sits noticeably higher than the other, by roughly a third of the column's height or more) with nothing in the shot (no tilt, added pressure, or blockage) to explain the difference; or the liquid in the tube looks like something other than water, such as opaque, metallic, or granular material.
level_2: Water is present, but it behaves in a way real hydrostatics forbids: one column keeps rising while the other keeps falling with no outside cause; the water keeps flowing long after the tube should have settled; or the two surfaces bob up and down repeatedly without ever settling toward a resting level.
level_3: Once the water stops moving, the two columns sit level with each other and neither surface is still moving; the water reads as transparent with a visible curved meniscus at each surface; its color is consistent with plain water (colorless or only very faintly tinted); nothing in the frame (pump, syringe, tilt) explains any height difference, because none remains.
level_4: The two water surfaces are level with each other and motionless as described above, and in addition each meniscus curves downward toward the tube's centerline (consistent with water wetting glass), no air bubble is trapped at the bottom bend breaking the connection between the two arms, and each surface is smooth, without ripples or foam.
level_5: The two surfaces are level, still, concave, and free of trapped air as described above, and in addition the bottom bend joining the two arms is fully visible and unobstructed so the shared body of water clearly forms one continuous path with no gap splitting the two columns; the leveling happens on its own once the water stops being added, and both surfaces stay level for the rest of the clip.

Spatiotemporal Consistency rubric:
level_1: The U-tube vanishes and reappears between frames, or the two water columns instantly jump from one height to another with no visible flow connecting the two states; the lighting suddenly flips from deep shadow to full brightness with no visible cause; the tube's outline itself warps or fractures from one frame to the next.
level_2: The U-tube stays visible, but its glass appears to bend, stretch, or collapse in a way real glass would not; a water column blinks out of existence and back between frames; the lighting shifts abruptly with no camera movement or environmental cause; the camera viewpoint jumps, such as cutting from a close-up to a wide shot with no transition.
level_3: The U-tube stays fixed in position and orientation for the entire clip; both water columns hold a stable position relative to the tube and the tabletop; the shadow the tube casts on the table keeps a consistent direction and softness throughout; the tube's shape and the water's appearance carry over continuously from frame to frame with no sudden breaks.
level_4: The tube, columns, and shadow stay as stable as described above, and in addition, if water is shown being poured in, that inflow moves smoothly and plausibly with no splashing, stuttering, or frame-to-frame jumps; no visible jitter, warping, or perspective shift appears anywhere in the clip.
level_5: The scene holds together as described above, and in addition the tube's centerline stays parallel to the frame's vertical edges in every frame, both water surfaces stay parallel to the tabletop throughout, and no motion blur is heavy enough to hide the columns' relative heights or their alignment with each other.