Domain: Engineering — Materials Science & Engineering
Target concept: Creep of Acrylic Rods in the Rubbery State Under Suspended Load

Video generation prompt: Suspend two identical transparent acrylic rods and hang identical metal weights at their lower ends; heat only the right rod while keeping the left rod at room temperature.

Evaluation guide:
(i) Target concept: Temperature-accelerated viscoelastic creep in amorphous thermoplastics above Tg.
Minimum mechanism: Acrylic must be above its glass transition temperature (~105°C) to enter the rubbery state where chain slippage under sustained stress becomes observable within seconds; room-temperature rod must remain below Tg to stay glassy and dimensionally stable.
(ii)Storyline: [Frame 0–2] Two identical acrylic rods suspended vertically, parallel, side-by-side; identical weights attached and motionless. [Frame 3–4] Heat source activates exclusively near right rod (visible cue: air shimmer, focused glow, or directional airflow). [Frame 5–8] Right rod exhibits progressive, monotonic downward extension at loaded end (increasing gap between support and weight) while left rod shows zero deformation. [Frame 9–10] Deformation stabilizes or continues smoothly; both rods remain optically transparent, structurally intact, and spatially fixed in view. Perspective: Fixed frontal orthographic view; full rods and weights always fully visible; no occlusion; lighting uniform and directional to reveal sag and transparency.

Manual:
Experimental Procedure
1. Suspend two identical transparent acrylic rods side-by-side from fixed supports.
2. Hang identical metal weights from the lower ends of both rods.
3. Apply heat only to the right rod (e.g., via hot air stream or IR lamp) while leaving left rod at room temperature.
Observation of Experimental Phenomena
The right rod gradually sags/elongates at its loaded end; the left rod remains straight and unchanged in length and shape.
Summary of Experimental Principles
Acrylic in the rubbery state exhibits time-dependent viscoelastic deformation (creep) under constant load; elevated temperature accelerates molecular chain mobility, increasing creep rate—hence only the heated rod deforms.

Prompt Grounding rubric:
level_1: Fewer than two rods are shown, or no metal weight hangs from either rod, or the two rods are not positioned side by side, or no heat source (flame, hot-air jet, lamp, etc.) is shown acting on either rod.
level_2: Two rod-shaped transparent objects hang side by side, but at least one is clearly not acrylic (looks like glass, plastic tubing, or bare wire); the two hanging weights differ from each other in size, shape, or material; the rods are not aligned next to one another; or the heat is aimed at the left rod, the background, or nothing at all.
level_3: Two identical clear acrylic rods hang side by side, each with an identical metal weight suspended from its lower end; a heat source (hot-air jet, lamp, or similar) is directed only at the right rod, with the left rod showing no sign of heating; the camera viewpoint stays fixed throughout.
level_4: Everything required for a 3 also holds; in addition, the heating is confined visibly to the right rod alone, with no glow, shimmer, or airflow reaching the left rod or its surroundings; both rods hang steady without swinging or coming loose, and both weights stay fully attached while the right rod heats.
level_5: Everything required for a 4 also holds; in addition, the heating begins only after both rods are already hanging with their weights attached; the heat cue (shimmer, glow, or visible heat-source activation) stays confined to the right rod's middle-to-lower section while the left rod looks completely undisturbed; and no step happens out of order (e.g., a weight appearing before its rod is hung, or heating starting before both rods are fully set up).

Scientific and Causal Correctness rubric:
level_1: Neither rod changes shape at all, or both rods stay rigid, straight, and identical throughout, showing no difference in sagging, bending, or stretching between the heated and unheated rod.
level_2: One or both rods deform, but the amount of sag or stretch looks the same on both sides; or the deformation shows up on the left (unheated) rod instead of the right; or what happens looks like a sudden snap, buckle, or sideways kink rather than a slow downward stretch.
level_3: The right rod visibly stretches downward at its loaded end (the gap between the rod's top support and its weight grows) while the left rod keeps its original length and stays straight; neither rod melts, discolors, or loses its transparency; the right rod's stretching is gradual and continuous, not sudden or jerky.
level_4: Everything required for a 3 also holds; in addition, the right rod's stretching is concentrated near the weighted end rather than spread evenly along its length; the left rod shows no measurable sag or curve at all; neither rod changes color, clouds over, or develops surface texture; and the weight stays firmly attached to the stretching right rod without slipping.
level_5: Everything required for a 4 also holds; in addition, the right rod's downward stretch proceeds smoothly and continues in one direction, without pausing, reversing, or oscillating; the left rod stays exactly as it was in shape, position, and clarity; and nothing else in the shot (camera movement, parallax, or a moving shadow) creates the false impression of sag.

Spatiotemporal Consistency rubric:
level_1: A rod or its weight jumps to a different position between frames with no motion shown in between; a rod shows a sudden break, gap, or splice in its length; the lighting or shadow on one rod changes suddenly and without cause; a rod or weight flickers, disappears, or reappears; or the camera viewpoint suddenly shifts or rotates.
level_2: A rod's thickness changes partway along its length without a smooth taper; a weight detaches and then reattaches; the shadow cast by a rod swings to a different direction with no matching change in the light source; a rod appears to bend and then snap back straight with no motion in between; or the lower rod and weight are completely hidden from view for more than a second at a critical moment.
level_3: Both rods stay whole and unbroken cylinders throughout, and both weights stay fully visible and attached to their rods; the direction and strength of the light on the rods stays the same from the moment heating starts to the end of the clip; the camera viewpoint never shifts; and there is no tearing, duplication, or freezing of the image.
level_4: Everything required for a 3 also holds; in addition, the two rods stay parallel and the same distance apart throughout; each weight hangs straight down under its own rod with no weight passing through or overlapping a rod; and any sagging motion looks smooth and physically reasonable rather than floating or speeding up unnaturally.
level_5: Everything required for a 4 also holds; in addition, no frames are skipped or repeated, and the pace of the right rod's sagging neither speeds up nor slows down in an artificial way; the rod and weight edges stay sharp with no visible flicker, tearing, or duplication artifact (heat-shimmer air distortion near the heated section of the right rod is an expected part of the heating cue and is not counted as a flaw); and the light and shadow on the rods do not jump or discontinue at the moment heating begins.