Mechanical power and efficiency calculator

Constant translational force at velocity.

dynamics-mechanical-power.napkin / editable

SCENARIO COMPARISON

Compare the numbers.

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

Scenario	mechanicalW	inputW
	50	62.5
	40	50

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.

input power budget62.50 W✓ passes

BASELINE INPUTS

force100 Nspeed0.5 m/sefficiency0.8

CALCULATED

mechanical50 W

input62.5 W

Edits change the baseline source.

THE SOURCE

Edits below update the same model.

# Mechanical power and efficiency
# Scope: Constant translational force at velocity.
# Status: illustrative worked example; engineering review pending.
# Inputs are example values. Checks are editable example requirements, not standards.

force = 100 N
speed = 0.5 m/s
efficiency = 0.8

mechanical := force*speed [W]
input := mechanical/efficiency [W]

check input power budget: input <= 100 W

scenario alternative: force = 80 N

Calculated from your source · not saved

Baseline · Baseline

input power budget62.50 W ✓ passes

alternative · alternative

input power budget50.00 W ✓ 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.

mechanical: mechanical = force*speed [W]
input: input = mechanical/efficiency [W]

Original worked example

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

Given

force: 100 N
speed: 0.5 m/s
efficiency: 0.8

Calculated

mechanical: 50 W
input: 62.5 W

Assumptions and limits

Constant translational force at velocity.

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: Mechanical power and efficiency. Inputs: force and speed or torque and RPM; efficiency. Outputs: shaft power; input power; losses. 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: force and speed or torque and RPM, efficiency
Outputs: shaft power, input power, losses
Modes: calculate, compare, sweep
Drawing: Motion and load plots

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