Terminal Velocity Calculator

Inspectable records

Ledger state

The current ledger marks this instrument verified with errata that must be applied at binding time.

Area

Physics

Tranche

tranche-2

Evidence ID

t2-035

Ledger rows

1

No ledger note is attached.

Review findings

The mathematical formula is correct for steady quadratic drag with constant Cd. Before release, explicitly document or expose g, specify required units and validation constraints, and replace the laminar wording with an accurate statement such as 'assumes constant quadratic-drag coefficient, typically appropriate over a specified Reynolds-number regime.'

Formula and scope findings

• The formula v_t = sqrt(2mg/(rho Cd A)) is the standard terminal-speed formula for quadratic drag, assuming constant gravitational acceleration, constant drag coefficient, and SI-compatible quantities.
• The specification omits g from the listed inputs and does not explicitly state whether g is fixed at 9.81 m/s^2 or configurable; this is an exact implementation ambiguity.
• The honest label 'laminar-simplified drag' is misleading: quadratic drag is generally used at sufficiently high Reynolds number, while many laminar regimes are better modeled with linear Stokes drag.
• The spec does not define valid input constraints such as mass > 0, Cd > 0, cross-section area > 0, and air density > 0.

Unit assumptions

• mass is in kilograms
• cross-section area is in square metres
• air density is in kilograms per cubic metre
• Cd is dimensionless
• g is assumed to be the fixed standard value 9.81 m/s^2 unless explicitly made an input
• terminal velocity output is in metres per second

Boundary hardening

BREAK_CLAIMED · SELF_FLAGGED

The specification provides no stated validation behavior for zero or negative density, drag coefficient, or area, so the raw formula can produce division by zero or a non-real square root. It also returns only a speed magnitude, leaving the sign convention ambiguous. The formula has no true multi-regime branch, so a correct implementation must explicitly reject invalid-sign inputs rather than silently treating them as a second physical branch.

Errata and corrections

No applied erratum is attached to this unique-name record.

Inspectable example

4 review vectors are recorded. One source-bound sample is shown below.

{
  "inputs": {
    "mass": 0.1,
    "mass_unit": "kg",
    "Cd": 0.47,
    "area": 0.01,
    "area_unit": "m^2",
    "air_density": 1.225,
    "air_density_unit": "kg/m^3"
  },
  "expected_outputs": {
    "terminal_velocity": 18.46,
    "terminal_velocity_unit": "m/s"
  },
  "working": "Use g = 9.81 m/s^2. Numerator = 2 × 0.1 × 9.81 = 1.962. Denominator = 1.225 × 0.47 × 0.01 = 0.0057575. Ratio = 1.962 / 0.0057575 = 340.7729. Square root = sqrt(340.7729) = 18.4600 m/s, so terminal velocity ≈ 18.46 m/s."
}

Related workflows

No source-defined multi-instrument workflow membership is recorded.

Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

• VERIFIED_LEDGER.json · VERIFIED_WITH_ERRATA
• evidence-tranche2/tranche2-results.json
• BOUNDARY_HAZARD_CATALOG.json