Domain: Natural Science — Physics
Target concept: A charged balloon causes the thin stream of water from the faucet to bend.

Video generation prompt: A person charges a latex balloon by rubbing it against wool, then directs a thin stream of water from a faucet and brings the balloon close to the stream without touching it.

Evaluation guide:
(i) Target concept: Electrostatic induction in polar dielectric fluids (water) leading to macroscopic attraction.
Minimum mechanism: Balloon must acquire net charge via triboelectric transfer (wool → latex); water must remain electrically neutral overall but internally polarizable; no grounding path must exist between balloon and stream; stream must be laminar and thin enough for electrostatic force to overcome inertia and gravity.
(ii)Storyline: [Phase 1: Preparation] Wool and uninflated latex balloon enter frame; rubbing action begins and ends visibly. [Phase 2: Activation] Faucet turns on; thin vertical stream establishes. [Phase 3: Interaction] Balloon (now separated from wool) approaches stream laterally; stream begins bending *only after* proximity and *only while* balloon is held steady nearby. [Phase 4: Reversibility] Balloon withdraws; stream returns to vertical. Perspective: Fixed frontal view showing balloon, stream, faucet, and hands; all in same plane, no occlusion of key interaction zone (balloon-stream gap). Visibility constraint: Entire bending region (at least 2 cm of stream length near balloon) must be fully visible and unobstructed throughout Phase 3.

Manual:
Experimental Procedure
1. Rub an uninflated latex balloon vigorously against a piece of dry wool for 2 seconds.
2. Turn on faucet to produce a thin, steady, vertical stream of water.
3. Hold the rubbed balloon close to the stream (without touching) and observe.
Observation of Experimental Phenomena
The thin stream of water bends steadily toward the balloon as soon as the balloon is brought near, remaining bent while the balloon is held adjacent, and returning to vertical when the balloon is withdrawn.
Summary of Experimental Principles
Rubbing transfers electrons from wool to balloon, giving the balloon a net negative charge. The charged balloon induces polarization in the neutral water molecules, attracting the positive ends and causing the stream to deflect toward the balloon.

Prompt Grounding rubric:
level_1: No balloon present; no faucet or water stream visible; no person performing rubbing or holding action; none of the three core objects (balloon, wool, faucet) appear.
level_2: At least one core object appears (e.g., balloon OR faucet OR wool), but no sequence of actions matches the posted_prompt: e.g., balloon is shown static without rubbing, or water stream exists without balloon proximity, or rubbing occurs with wrong material (e.g., hair instead of wool).
level_3: All three core objects are present (latex balloon, wool fabric, faucet with water stream); rubbing action between balloon and wool is shown; balloon is then brought near water stream; but at least one of these actions lacks correct object association (e.g., rubbing performed on sleeve instead of wool, or balloon held near stream before rubbing, or faucet not visibly producing a thin continuous stream).
level_4: All three core objects are present and correctly identified by appearance (latex balloon: matte, slightly wrinkled, round; wool: fibrous, textured, off-white/beige; faucet: metallic, fixed, with downward vertical stream); rubbing occurs exclusively between balloon and wool; balloon is brought near (not touching) the stream *after* rubbing; stream originates from faucet and remains continuous throughout the proximity phase.
level_5: All conditions for score 4 are satisfied, AND the balloon is visibly held stationary adjacent to the stream (no contact), AND the wool is clearly detached from the balloon during proximity (i.e., wool not in frame or fully separated), AND the faucet, stream, balloon, and person's hand holding balloon all remain within a single fixed viewpoint without cut or repositioning.

Scientific and Causal Correctness rubric:
level_1: No observable interaction between balloon and water stream; stream flows straight regardless of balloon position; no bending or deflection occurs at any frame; balloon shows no charge-related behavior (e.g., no attraction to hair or wall if shown, but not required).
level_2: Stream bends in direction *away* from balloon (repulsion) OR bends only when balloon touches stream OR bending occurs before rubbing OR bending is inconsistent (e.g., bends left then right without cause).
level_3: Stream bends toward the balloon *after* rubbing, but bending is discontinuous (e.g., appears only briefly then vanishes), OR bending occurs while balloon is still in contact with wool, OR stream breaks into droplets *before* bending begins, OR balloon color/texture contradicts latex (e.g., shiny plastic or metallic surface).
level_4: Stream bends continuously and stably toward the balloon *only after* rubbing ceases and balloon is held adjacent; bending persists as long as balloon remains nearby; no contact occurs; stream remains intact (no splashing, breaking, or widening); balloon surface appears matte and deformable (consistent with latex), not rigid or glossy.
level_5: All conditions for score 4 are satisfied, AND bending magnitude is visually stable (no flickering, pulsing, or reversal), AND no competing phenomena occur (e.g., no electrostatic dust attraction, no unintended water splash, no stream oscillation unrelated to proximity), AND the bending direction is unambiguously *toward* the balloon across all visible frames of proximity.

Spatiotemporal Consistency rubric:
level_1: Severe continuity breaks: the balloon disappears from one spot and reappears elsewhere without visibly moving through the space between; the water stream vanishes and reappears with no visible cause; the faucet's position jumps; the room lighting swings abruptly from bright to dark or back; the hand holding the balloon disappears and returns gripping it in a different way.
level_2: Clearly noticeable flaws: the balloon spins or tumbles rapidly for no apparent reason; the stream appears to flow upward or sideways in defiance of gravity; a hand enters the shot at a scale that doesn't match its distance from the camera; the shadows cast by the balloon or faucet suddenly point a different direction partway through the clip; the water stream cuts on and off repeatedly instead of flowing continuously.
level_3: Small but visible flaws: the stream shows a brief, noticeable break or stutter in what should be continuous flow; the balloon wobbles back and forth well beyond what a steady hand-hold would cause; hand tremor makes the balloon's distance from the stream visibly inconsistent from moment to moment; background details such as the sink edge or faucet base appear to shift slightly between shots.
level_4: All motion looks physically natural: the balloon eases smoothly into position near the stream; the water flows as one continuous, laminar column throughout; the hand's movement is steady and matches how someone would actually hold and position a balloon; shadows cast by the balloon and hand point the same direction from the first frame to the last, and the sink area's brightness doesn't noticeably change; no object (faucet, balloon, hand) warps or deforms; no visible cuts break up the action.
level_5: Everything required at the 4-point level holds, and in addition the balloon's approach speed looks even, without sudden speeding up or slowing down; the gap between balloon and stream stays visually steady once the balloon is in position, without unexplained drifting closer or farther; the entire clip plays smoothly with no strobing, flicker, or ghost-trailing around moving edges.