Source: https://guthlabs.ai/docs/instruments/atwood-machine-solver/implementation/

instrument implementation / implementation-contract

# Atwood Machine Solver implementation

A source-bound implementation contract for Atwood Machine Solver; deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**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-clean

**Evidence ID**: t4-272

**Effect**: Computation or source lookup only

## Input and validation requirements

A nonzero pulley inertia combined with zero pulley radius makes I/r^2 undefined. Without explicit input validation, the solver can propagate undefined or nonfinite values into acceleration and tension instead of rejecting the input.

## 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": {
    "m1_kg": 2,
    "m2_kg": 5,
    "pulley_I_kg_m2": 0,
    "pulley_radius_m": 0.2,
    "g_m_s2": 9.81
  },
  "expected_outputs": {
    "acceleration_m_s2": 4.2042857143,
    "tension_m1_N": 28.0285714286,
    "tension_m2_N": 28.0285714286
  },
  "working": "I/r²=0/0.2²=0. Denominator=2+5+0=7 kg. Numerator=(5-2)×9.81=29.43. a=29.43/7=4.2042857143 m/s². T1=2×(9.81+4.2042857143)=2×14.0142857143=28.0285714286 N. T2=5×(9.81-4.2042857143)=5×5.6057142857=28.0285714286 N; with an ideal massless pulley, both tensions are equal."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/atwood-machine-solver/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/atwood-machine-solver/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/atwood-machine-solver/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-tranche4/tranche4-results.json`