Source: https://guthlabs.ai/docs/instruments/terminal-velocity-calculator/implementation/

instrument implementation / implementation-contract

# Terminal Velocity Calculator implementation

A source-bound implementation contract for Terminal Velocity Calculator; deployment and executable qualification remain separate.

Status: **VERIFIED_WITH_ERRATA**Lifecycle: **implementation-contract**

## Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

**Record owner**: Guth Instruments

**Lifecycle**: verified-with-binding-errata

**Evidence ID**: t2-035

**Effect**: Computation or source lookup only

## Input and validation requirements

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.

## Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

## Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

````
{
  "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."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/terminal-velocity-calculator/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/terminal-velocity-calculator/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/terminal-velocity-calculator/qualification/>)

## Sources and evidence

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

- `VERIFIED_LEDGER.json`

- `evidence-tranche2/tranche2-results.json`