Domain: Natural Science — Physics
Target concept: Inclined plane motion

Video generation prompt: Two smooth inclined planes are placed side by side on a horizontal table, with the left plane having an angle of 30° and the right plane an angle of 60°. Two identical cars are released simultaneously from the same height on the two smooth inclined planes.

Evaluation guide:
Target concept: Gravitational acceleration component on inclined planes (a = g*sin(theta)) governs motion dynamics -- specifically, how steeper inclines yield greater acceleration and shorter descent times for identical masses released from equal heights. Minimum mechanistic assumptions: (1) negligible friction (smooth planes), (2) uniform gravitational field, (3) rigid-body rolling without slip, (4) Newtonian mechanics applies. Expected phased storyline: (Phase 1) Static start -- two identical cars held at identical vertical height on 30-degree and 60-degree ramps; (Phase 2) Simultaneous release -- both begin moving downward at t=0; (Phase 3) Divergent acceleration -- right car's speed increases faster, creating a widening spatial gap that grows quadratically; (Phase 4) Asymmetric arrival -- the right (60-degree) car reaches the bottom well before the left (30-degree) car; because both are released from the same height rather than the same ramp length, the left car's descent takes roughly 1.7 times as long (about 70-75% longer) than the right car's, confirming t is proportional to 1/sin(theta). Visibility constraints: must capture full side profile with orthogonal camera; height alignment and angle distinction must be visually verifiable via geometry (e.g., height/base ratios) or on-screen labels; simultaneity must be unambiguous (no perceptible delay); no occlusion of motion path or release point.

Manual:
I. Basic Demonstration Information
Demonstration Title: Comparative Acceleration on Smooth Inclined Planes (30 degrees vs. 60 degrees) Demonstration
Subject: Natural Science - Physics - Inclined Plane Motion
Demonstration Purpose: By releasing two identical cars simultaneously from the same height on two smooth inclined planes (left: 30 degrees, right: 60 degrees), this demonstration visually reveals how the gravitational acceleration component (g*sin(theta)) governs motion -- enabling direct comparison of acceleration magnitude, speed development, and descent time; it establishes empirical grounding for Newton's second law on inclines and reinforces quantitative reasoning about the trigonometric dependence of forces.

II. Demonstration Carrier/Equipment
Core Carrier: Two identical low-friction toy cars (metallic gray, 4-wheel, symmetrical, mass-matched +/-1g)
Smooth Inclined Planes: Two rigid, straight, matte-finish acrylic ramps (length >= 1.2m), mounted side-by-side on a level horizontal table; left ramp angle precisely 30 degrees, right ramp angle precisely 60 degrees (verified by digital inclinometer or geometric calibration); surfaces polished to eliminate rolling resistance cues.
Auxiliary Equipment: Horizontal table (stable, non-vibrating, matte black surface); release mechanism (dual synchronized gate or fingertip release at marked height line); vertical height reference (laser level or calibrated tape marking identical y-coordinate on both ramps); side-view camera (fixed, orthogonal to plane direction, full-frame capture).

III. Demonstration Content Description
Layout: Place ramps flush against table edge, parallel and adjacent (gap <=1cm), sharing a common base line; ensure the table is level (bubble level verified). Mark an identical release height (e.g., 40cm vertical from table) on both ramps using a horizontal laser line.
State Control: Cars placed stationary at the release line, wheels aligned, no pre-rotation; surfaces dust-free; ambient lighting uniform and glare-free.
Comparison Baseline: Identical cars ensure mass/inertia equivalence; the same height ensures equal initial gravitational potential energy (mgh); differing angles isolate theta as the sole variable.

IV. Observation of Core Phenomena
Initial State: Both cars motionless at identical vertical height; ramps static; no external force applied.
Motion Onset: Simultaneous release leads to immediate downward acceleration on both planes; no delay or hesitation.
Acceleration Divergence: The right (60-degree) car rapidly pulls ahead -- its speed increases faster; the spacing between cars widens progressively and quadratically over time.
Terminal State: The right (60-degree) car reaches the bottom well before the left (30-degree) car -- consistent with equal release height, the left car's total descent time is roughly 1.7 times the right car's (about 70-75% longer); both cars stop upon hitting identical end buffers with no rebound.
Visual Feature Recognition Comparison: The left plane exhibits a gentle slope (height/base ratio of about 0.58), the right plane a steep one (height/base ratio of about 1.73); car trajectories are straight, parallel to their respective ramps; shadows confirm lighting consistency and the downward motion direction; the absence of skid marks or bounce confirms smoothness.

V. Summary of Key Knowledge Points and Principles
Core Concept Definition: On a frictionless incline, the acceleration of an object is a = g*sin(theta), where theta is the angle between the plane and the horizontal -- independent of mass, dependent only on gravity and geometry.
Causal Mechanism: The component of gravitational force parallel to the plane (F_parallel = mg*sin(theta)) determines the net force, producing acceleration a = F_parallel/m = g*sin(theta). Hence larger theta gives larger sin(theta) gives larger a. For a fixed ramp length L, descent time t = sqrt(2L/(g*sin(theta))), which is proportional to 1/sqrt(sin(theta)); but here both ramps are released from the same height h rather than the same length, so the ramp length L = h/sin(theta) differs between ramps, giving t = sqrt(2h/g)/sin(theta), proportional to 1/sin(theta). This yields t_left/t_right = sin(60)/sin(30) = approximately 1.73, i.e. the 30-degree car takes about 73% longer than the 60-degree car.
Verification Logic: Same height means same mgh means the same kinetic energy at the bottom, hence the same final speed v = sqrt(2gh) for both cars regardless of angle. Despite reaching the same final speed, the two cars take different times to arrive because their accelerations (g*sin(theta)) and ramp lengths (h/sin(theta)) differ: the 60-degree ramp delivers about 1.73 times greater acceleration than the 30-degree ramp, so its car arrives first even though both would be moving at the same speed at the very bottom.

VI. Demonstration Precautions
Angle Calibration: Verify angles before recording using an inclinometer or trigonometric measurement (height and base measured to +/-0.2cm); reject if deviation exceeds +/-1 degree.
Synchronization: Use a mechanical dual-gate or high-speed trigger to ensure release simultaneity; avoid manual release unless high-speed validation confirms alignment.
Smoothness Guarantee: Polish ramps; test with slow-motion playback -- no wheel slippage, no vibration, no audible friction sound.
Viewing Geometry: Camera must be perpendicular to the plane direction and at mid-height to avoid parallax; field of view includes the full ramp length and base.
Timing Constraint: Keep video duration to about 10s -- accelerate playback only if needed for clarity, but preserve the causal sequence and relative timing fidelity.

Prompt Grounding rubric:
level_1: No inclined planes are shown; no cars appear; there is no horizontal table; the two ramps are not arranged side by side; the ramps show no distinguishable angle difference (e.g., both look vertical, or both look like curved surfaces); the two cars look different from each other (different color, size, or shape); one car starts noticeably higher than the other; only one car ever moves, or there is an obvious pause of half a second or more between the two cars starting.
level_2: Two ramps are present but their slopes look nearly identical, with no visible or labeled way to tell which is 30 degrees and which is 60 degrees; the table's horizontal surface is not clearly established; the two cars look similar but differ in some visible detail (wheel style, trim color); the two release heights are visibly different, with one car starting noticeably higher up its ramp than the other; the two cars start moving at clearly different moments.
level_3: Two smooth ramps sit side by side on a flat table, and the left one visibly looks shallower than the right one; the two cars are identical in shape and color; both cars are released from what looks like the same height (e.g., their starting marks line up), but there is nothing in frame (no angle labels, no grid) confirming the ramps are actually 30 and 60 degrees; the two cars appear to start moving at close to the same instant, though a slight lag is noticeable if watched carefully.
level_4: Two rigid, straight ramps sit side by side on a level table; the left ramp is visibly shallow (consistent with about 30 degrees) and the right is visibly steep (consistent with about 60 degrees), supported by a height-to-base proportion or an angle label in frame; the two cars are identical (same body, color, wheels); both are released from a marked line at the same height on their respective ramps; the two cars begin moving together, with no perceptible gap between the two start times.
level_5: Every setup detail matches precisely: (i) the left ramp's rise-to-run proportions are consistent with 30 degrees and the right ramp's with 60 degrees, either through a drawn angle guide or a clearly proportioned height/base relationship; (ii) both ramps look equally smooth and rigid, sitting flush against the same base line; (iii) the two cars are visually identical in body, color, and wheels; (iv) both cars sit at the same marked height line before release; (v) both cars are released as a single visible action (such as a hand or gate releasing both at once) with no noticeable gap between the two cars beginning to move, and nothing in frame blocks the view of either car's path.

Scientific and Causal Correctness rubric:
level_1: One or both cars move upward or sideways instead of down their ramp; the two cars accelerate identically despite the different ramp angles; the car on the steeper (60-degree) ramp moves slower than the one on the shallower (30-degree) ramp, or stops partway down; neither car shows any speeding-up as it descends; nothing about the motion suggests gravity is pulling the cars down their ramps.
level_2: Both cars roll downward, but the left (30-degree) car ends up accelerating faster than the right (60-degree) car, which is backward from what the physics predicts; the two cars reach the bottom at the same time despite the different angles; the right car pauses or stutters partway down; the cars' speeds don't visibly increase as they descend; there's no visible connection between which ramp is steeper and which car is moving faster.
level_3: Both cars start from rest and speed up as they go down; the right (60-degree) car is moving noticeably faster overall and reaches the bottom first, consistent with the steeper ramp giving it a stronger push; the left (30-degree) car is slower and arrives later; the speeding-up looks steady rather than jerky, but there's no visible sense of the gap between the cars growing over the course of the descent -- the difference in arrival time is the only cue used.
level_4: The gap between the two cars visibly grows as the descent continues -- early on the cars are close together, and partway down the right car has clearly pulled ahead, with the lead continuing to widen until it reaches the bottom well before the left car; both cars' motion looks smoothly accelerating throughout, with no sudden jerks or coasting at constant speed; the two ramps' bases line up so the arrival gap is easy to see; the left car's descent visibly takes noticeably longer than the right car's -- roughly 1.7 times as long (about 70-75% longer), consistent with equal release height and the two ramp angles.
level_5: The full picture matches the physics of equal-height release on different slopes: (i) the right (60-degree) car visibly accelerates faster than the left (30-degree) car -- its speed increases more briskly, consistent with the steeper ramp's larger gravity component along the slope; (ii) the gap between the two cars grows at an increasing rate rather than a constant one, reflecting accelerating (not constant-velocity) motion for both; (iii) neither car shows signs of air drag or rolling resistance (no leveling-off of speed, no odd wobble); (iv) both cars travel strictly along their own ramp's direction with no sideways drift or bouncing; (v) the right car reaches the bottom well before the left car, with the left car's total descent time roughly 1.7 times the right car's (about 70-75% longer) -- matching the correct physics for two ramps of different angles released from the same height.

Spatiotemporal Consistency rubric:
level_1: A ramp appears to float without any visible support; a car appears to hover above the ramp surface instead of resting on it; the table looks tilted or warped; the shadows cast by the ramps or cars point in conflicting directions as if lit from different sides; a car casts no shadow at all while everything else does; the video jumps abruptly between moments, freezes for a long stretch, or a car disappears from one point on its ramp and reappears elsewhere without covering the distance between.
level_2: The two ramps are anchored to the table but the camera's perspective makes them look like they're not actually parallel; shadows are cast in a direction that doesn't match a single consistent light source; a car appears to float slightly or bounce oddly against the ramp surface; the video shows brief jitter or a couple of dropped frames; there's a visible skip between the cars sitting still and being partway down the ramp, missing the beginning of the acceleration; a car's apparent size changes noticeably as it moves.
level_3: The ramps look solidly fixed to the table, and the shadows roughly match a consistent light source; both cars stay in contact with their ramp surfaces throughout; the perspective shows mild, natural foreshortening rather than an obvious distortion; the motion is continuous, but there is occasional slight vibration or unevenness in a car's path; the overall pacing and progression of the descent is plausible without major violations of how objects should move.
level_4: The two ramps appear parallel and consistently positioned in depth; the shadows fall consistently downslope from a single overhead or frontal light source; each car keeps a constant size, orientation, and contact with its ramp throughout the descent; each car's path is a straight line along its own ramp with no sideways wandering; the video plays smoothly with no flicker or visible frame-blending artifacts; the pacing of the descent looks physically natural throughout, speeding up steadily rather than in fits and starts.
level_5: The whole sequence holds together with no visible flaws: (i) both cars stay in continuous contact with their ramp surfaces, with no wheel slip, sinking into, or lifting off the surface; (ii) the lighting comes from one consistent, steady source, casting shadows that stay aligned with each ramp's slope and stay visually proportionate to how shallow or steep that ramp is (the shallower 30-degree ramp's shadow reading noticeably longer than the steeper 60-degree ramp's); (iii) the camera holds a single fixed, front-on view that captures the table, both full ramps, and each car's entire path with nothing cut off; (iv) both cars' paths stay perfectly straight along their own ramp's direction; (v) each car's position advances smoothly frame to frame with no visible jumps, freezes, or reversals, consistent with the car continuously speeding up as it slides down.