Domain: Natural Science — Physics
Target concept: Gently submerging a floating ping-pong ball into water and releasing it verifies that the ball immediately rises back to the surface and resumes its floating state, exhibiting distinct visual characteristics.

Video generation prompt: A transparent container is filled with clear water. A dry ping-pong ball floats on the water surface. A hand gently presses the ping-pong ball vertically downward into the water and then releases it. The camera remains fixed, clearly capturing the entire motion of the ping-pong ball from the moment it is pressed down to the moment it is released.

Evaluation guide:
(i) Target concept: Net upward acceleration due to unbalanced buoyant force upon release from forced submersion.
Minimum mechanism: Ball must be less dense than water, hollow, air-filled, impermeable, and rigid enough to retain shape; water must be static, incompressible, and exhibit surface cohesion; gravity and fluid pressure gradient must be implicitly active.
(ii)Storyline: [Start] Stable floating ball on calm water surface → [Trigger] Hand enters frame, contacts ball top, applies vertical downward force → [Transition] Ball descends continuously, fully submerging, displacing water → [Release Point] Hand fully withdraws → [Causal Response] Ball immediately accelerates upward (no latency) → [Rise Phase] Ball ascends continuously along vertical line, water dimpling recedes, surface ripples propagate outward → [Termination] Ball breaches surface, settles, and resumes motionless float with no residual oscillation. Perspective: Fixed frontal/side view showing full vertical extent; all events must be fully visible without occlusion, cropping, or angle ambiguity.

Manual:
Experimental Procedure
1. Place a transparent container (e.g., glass tank) on stable surface and fill with clear water to ~80% height.
2. Gently place a dry white ping-pong ball on water surface so it floats motionlessly.
3. Position camera directly facing side or front, fixed and steady, capturing full vertical motion range.
4. With bare hand, gently press ball straight down vertically until fully submerged, then instantly release.
Observation of Experimental Phenomena
- Ball floats stably before pressing.
- Ball moves downward continuously during press.
- Ball remains fully submerged for brief moment after release.
- Ball rises continuously and directly upward, breaking surface, and resumes stable floating at original position/orientation.
Summary of Experimental Principles
Buoyant force exceeds gravitational force on the ping-pong ball; net upward acceleration occurs upon release because F_buoyancy > F_gravity, causing immediate upward motion until equilibrium at surface.

Prompt Grounding rubric:
level_1: No transparent container is visible; no clear water is shown; no ping-pong ball appears at any point; no hand is present; neither a downward press nor a release action occurs; the scene bears no visual relation to a floating ball being submerged.
level_2: At least one of the four required elements (transparent container, clear water, dry ping-pong ball, human hand) appears, but fewer than three of them are simultaneously present in a coherent arrangement; the ball is never shown floating on the surface before any hand contact; a press-down action, a release action, or both are absent or cannot be identified.
level_3: A transparent container holds clear water; a dry white ping-pong ball floats on the surface at the start; a human hand enters frame and contacts the ball from above; the hand presses the ball downward from the surface into the water; the hand then withdraws while the ball is still below the surface; all four objects and the press-then-release sequence occur in the correct temporal order.
level_4: All conditions for score 3 are met, AND the ball sits entirely above the waterline before the hand makes contact; the hand's contact and downward motion are vertical only, without lateral dragging or tilting of the ball; the ball becomes fully submerged (no portion visible above the surface) at the point of maximum depression; the hand completes its withdrawal before the ball is shown moving upward; the camera holds a single fixed framing that keeps the full press-to-submersion path inside the visible frame.
level_5: All conditions for score 4 are met, AND the ball floats without drifting, spinning, or wobbling before the hand touches it; the press and release are performed as one unbroken hand motion, with no pause, re-grip, or second contact; the hand clears the water and exits the ball's immediate vicinity at the moment of release, leaving the ball unobstructed for the remainder of the shot; the entire sequence is captured in a single uncut take with no cut, zoom, or camera reposition.

Scientific and Causal Correctness rubric:
level_1: The ball sinks and stays submerged, or floats below the surface without returning to it; the ball visibly dissolves, deforms, or disintegrates; the ball changes color or transparency; the water turns opaque, murky, or colored; no buoyant rise occurs after release at all.
level_2: The ball rises only partway and stalls before reaching the surface (e.g., stays half-submerged); the ball rises and then sinks back down with no new hand contact; the ball's rise is accompanied by air bubbles escaping from inside its shell, implying the shell has been punctured; the ball's upward motion abruptly decelerates or reverses direction with no external cause; the water level visibly drops or surges in a way inconsistent with the ball's small displacement.
level_3: The ball rises continuously after release and fully re-emerges to float on the surface, with no sinking or hovering below the surface at any point; the ball stays dry-white and intact throughout; the water stays clear and still except for the localized disturbance caused by the ball's own motion; the rise begins immediately when the hand withdraws, with no delay.
level_4: All conditions for score 3 are met, AND the ball does not deform, rotate, or spin while submerged or while rising; no unnatural surface-tension effect is visible, such as a sheet of water clinging to the ball or a dimple around it that fails to close; the ball's upward path stays vertical and aligned with the direction it was originally pressed; the ball shows no secondary bobbing or oscillation once it comes to rest on the surface.
level_5: All conditions for score 4 are met, AND the ball resumes the same floating orientation and position it had before pressing, with no lasting drift or tilt; the water surface returns to a calm, undisturbed state within the same shot, leaving no persistent ripple or distortion around the ball; the ball's rise speed increases smoothly from zero at the moment of release, without a jerky start, a constant-velocity coast, or a slowdown before reaching the surface.

Spatiotemporal Consistency rubric:
level_1: The ball vanishes and reappears at a different depth with no visible motion connecting the two positions; the hand appears or disappears abruptly rather than entering or exiting through the frame edge; the water's surface jumps to a different level or fractures without a continuous ripple; the container's walls visibly warp or flicker; the shadow cast by the ball or hand disappears in one frame and reappears later with no continuous transition.
level_2: The ball's motion is jerky or stutters, with visible skips along its downward or upward path; the hand's motion contains visible cuts or duplicated, layered frames; the water's reflections or refractions change inconsistently from one frame to the next; the container's edge bends or wobbles without cause; the ball flickers or momentarily disappears while it is in motion.
level_3: The ball follows one continuous, visible path from the surface down to full submersion and back up to the surface; the hand enters, contacts, presses, withdraws, and exits the frame without disappearing or jump-cutting; the water surface deforms locally under the ball's pressure and rebounds smoothly in a way that is consistent from frame to frame; the container stays rigid and stationary throughout; the direction and brightness of the light source and the shadows it casts stay the same from the first frame to the last.
level_4: All conditions for score 3 are met, AND the sharpness of the ball matches the sharpness of the water around it, with no mismatched blur between the two; the ball's outline and the container's edge stay aligned from one frame to the next with no sudden shift; events occur in the correct physical order (the hand withdraws only after releasing the ball, and the ball's upward motion begins only after the hand has cleared it); the camera shows no parallax shift or perspective change that would indicate the camera itself moved.
level_5: All conditions for score 4 are met, AND the ball's leading and trailing edges stay equally sharp throughout its motion, with no duplicated or ghosted outline trailing behind it; the ripple pattern spreading out from where the ball contacts the water is even in all directions, expanding outward without gaps or sudden jumps; the reflections and refractions on the container match the ball's actual position and the scene's lighting at every point in the shot; no frame shows a mismatched or doubled edge on the ball or the water's surface.