PARTIAL: for an object released from rest in ideal free fall, speed after selected time t is v = gt and drop distance is h = gt²/2. If that speed is then reduced uniformly to zero over selected distance s, the average upward support force during the stop is F = m[v²/(2s) + g]. This preserves a bounded energy calculation but does not reconstruct a safety-tackle mechanism or predict peak force.
PARTIAL · Ideal Free-Fall and Constant-Stop Model
Compare ideal average support force for two selected constant-deceleration stopping distances after a selected free-fall interval.
Equation Used
- The selected mass is released from rest in constant gravitational acceleration g = 9.81 m/s².
- The stop begins after the selected free-fall interval.
- Deceleration is constant over each selected positive stopping distance.
- Compliance, impact peaks, device geometry, strength, controls, redundancy and regulations are excluded.
PARTIAL: safety-tackle device geometry and motion remain unresolved. Do not use this model to size, certify, test or approve load-handling or fall-arrest equipment.
Two-stage ideal motion model
The visual separates free fall from the subsequent stop. During free fall, the selected load starts from rest and accelerates under constant gravitational acceleration. At engagement, the calculated speed becomes the initial speed for a separate constant-deceleration stop.
Two stopping distances are compared. The shorter selected distance produces the larger average support force. No ratchet, pawl, rope, chain, brake, spring, frame or control geometry is represented.
What the calculator determines
Select mass, free-fall time and two stopping distances. The calculator returns ideal engagement speed, ideal free-fall distance, and the average upward support force required for each constant-deceleration stop.
It does not calculate peak force, shock amplification, equipment capacity, permissible drop, stopping reliability, component stress, anchor load, human fall-arrest force or regulatory compliance.
Ideal work–energy identities
With release from rest and constant g = 9.81 m/s², v = gt and h = gt²/2. Constant stopping acceleration has magnitude a = v²/(2s). From vertical force balance during the stop, average upward support force is F = m(a + g) = m[v²/(2s) + g].
Stopping distance begins at engagement and must be positive. The displayed force is an ideal average over that distance; a real transient peak can be materially higher.
Selected-input example
For 500 kg released from rest for 0.50 s, the ideal engagement speed is 4.905 m/s and the free-fall distance is 1.226 m. A uniform stop over 80 mm requires an average upward support force of about 80.1 kN; over 50 mm it is about 125.2 kN.
These results follow only from the entered idealized motion. They do not establish that any device can arrest the load.
Scope and safety boundary
The original arithmetic is retained because it is dimensionally valid for a two-stage ideal model. Its former labels and surrounding article implied device-specific trip behavior, brands, applications, clearances, materials, inspection intervals, drop tests and safe use without supporting evidence.
Those claims and the unrelated actuator section are removed. Load handling and fall arrest are safety-critical: use the equipment manufacturer's instructions, applicable regulations and a qualified professional. Do not use this calculator to size, certify, test or approve equipment.
Questions
Is the result a peak arrest force?
No. It is the average upward support force for an assumed constant-deceleration stop.
Does free-fall time include the stopping interval?
No. The two stages are separate; stopping begins after the entered free-fall interval.
Does the model rate a safety tackle, hoist or anchor?
No. It contains no device geometry, material, strength, dynamics, wear, redundancy or failure analysis.
Can it be used for personnel fall arrest?
No. It is not a human-body, harness, lanyard, energy-absorber or regulatory-compliance model.
Technical references
- OpenStax University Physics, Work–Energy Theorem — kinetic-energy and work relationships.
- NIST Special Publication 811 — SI units and coherent quantity notation.
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