Impact force estimate calculator

Energy-equivalent average stopping force; peak force is not predicted.

dynamics-impact.napkin / editable

SCENARIO COMPARISON

Compare the numbers.

This source describes an analytical model. Its quantities and checks are the view.

Scenario	energyJ	averageForceN
	2	400
	1.6	320

All calculated quantities are listed with the inputs. Switch to Source to inspect the equations.

SCENARIOS / CALCULATED VALUESSAME SOURCE

Change an input to see the consequences.

average force budget400.00 N✓ passes

BASELINE INPUTS

mass1 kgspeed2 m/sstoppingDistance5 mm

CALCULATED

energy2 J

averageForce400 N

Edits change the baseline source.

THE SOURCE

Edits below update the same model.

# Impact force estimate
# Scope: Energy-equivalent average stopping force; peak force is not predicted.
# Status: illustrative worked example; engineering review pending.
# Inputs are example values. Checks are editable example requirements, not standards.

mass = 1 kg
speed = 2 m/s
stoppingDistance = 5 mm

energy := mass*speed^2/2 [J]
averageForce := energy/stoppingDistance [N]

check average force budget: averageForce <= 500 N

scenario alternative: mass = 0.8 kg

Calculated from your source · not saved

Baseline · Baseline

average force budget400.00 N ✓ passes

alternative · alternative

average force budget320.00 N ✓ passes

Illustrative first-order example. Checks are editable requirements, not design standards. The broader topic may require additional equations, data, and validation.

Formula and units

This example uses the following equations. Input names and units match the editable source above.

energy: energy = mass*speed^2/2 [J]
average force: averageForce = energy/stoppingDistance [N]

Original worked example

These are the baseline values in the downloadable source. Edits above let you test your own values.

Given

mass: 1 kg
speed: 2 m/s
stopping distance: 5 mm

Calculated

energy: 2 J
average force: 400 N

Assumptions and limits

Energy-equivalent average stopping force; peak force is not predicted.

The requirement checks use the limits written in this example. Passing a check does not establish that the model covers every load, material behavior, or operating condition in a real design.

Download this .napkin example ↓

Take it further with your agent

Napkin keeps the inputs, equations, checks and assumptions together in one study. Your agent sets it up; you change the numbers.

Try with Claude ↗

codex 'Use Napkin (https://napkin.engineering/mcp, or the local Napkin plugin) to build a study: Impact force estimate. Inputs: impact energy; stopping distance or stiffness. Outputs: average force; conditional peak estimate. Model scope: Rigid-body dynamics with stated force and motion profiles. Read napkin_capabilities and the current snapshot. Ask me for the values that matter, label assumptions with units, author .napkin source, validate it and apply it with napkin_source using the current revision, then open the study. Add checks for the limits I supply. Keep unsupported analyses explicit.'

Claude needs the Napkin connector; Codex needs the Napkin plugin. Set up your agent ↗

The broader study

The topic brief below describes the broader scope. The worked example above states the particular calculation it implements.

Inputs: impact energy, stopping distance or stiffness
Outputs: average force, conditional peak estimate
Modes: calculate, compare, sweep
Drawing: Motion and load plots

EXECUTABLE WORKED EXAMPLE · FIRST-ORDER MODEL · CHECK THE SCOPE & ASSUMPTIONS