Fix/potential energy reference height#315
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mattqdev merged 2 commits intoMay 16, 2026
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The drawLabel method in ForceRenderer hardcoded "N" (Newtons) as the
unit suffix for all vectors. In BallAcceleration, the acceleration
vector is drawn with F/m values (m/s²), so the label incorrectly
displayed "Acceleration (X.XN)".
Added a `unit` option to drawLabel so callers can override the default
"N". BallAcceleration now passes `{ unit: "m/s²" }` to drawVector,
fixing the label to correctly show "Acceleration (X.Xm/s²)".
getPotentialEnergy(gravity, referenceY) computes mass * g * (position.y - referenceY). The previous referenceY of toMeters(p.height) is the canvas top in Y-up coordinates, making PE almost always a large negative number. Changed referenceY to size/2 (ball center Y when resting on the floor), so PE correctly equals 0 at ground level — consistent with BouncingBall.
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🔍 Description
Problem
getPotentialEnergy(gravity, referenceY)computesmass × g × (position.y − referenceY).In
BallGravity.jsx,referenceYwas set totoMeters(p.height)— whichis the top of the canvas in Y-up coordinates (a large positive number).
Since the ball's Y position is always below the canvas top, this made PE
almost always a large negative number, which is physically incorrect.
Fix
Changed
referenceYtosize / 2— the ball center's Y position whenresting on the floor. This means PE = 0 at ground level, which is the
standard physics convention and consistent with how
BouncingBall.jsxalready handles it.
Closes #BUG-007 (if applicable)
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