The golden rule of mechanics

Содержание и основные понятия

Back to the table of contents
Alterna · physics · 4.3
The golden rule of mechanics
Continuation of work, SAP of mechanisms
Free cheese only happens in a mousetrap. No mechanism wins a job: how many times we win, we lose so much at a distance.
GEF · Grade 7
PIF · Baseline
01
The golden rule of mechanics
Wins in power = lose in distance.
The golden rule of mechanics
No simple mechanism can win a job.
The number of times we win is that we lose at distance so many times.
A₁ = A₂   →   F₁·s₁ = F₂·s₂
If the lever is 3 times the force (F2 = 3F1), the point of application of force F1 passes 3 times that (s1 = 3s2).
⚙
The Golden Rule of Mechanics (Visualization)
Animation: F1·s1 = F2·s2 / Rush / Block / Slope plane
Mechanism:
Winner is on:
3
x
02
SAP mechanism
Not all work is useful, part is lost.
SAP
Use-use factor (LAC)
- it's a relationship of good work to wasted work.
η = A
Got it.
/ A
morning
· 100%
A useful job is the one that uses the machine, and it's the full job that the machine has done.
The PAC is always < 100 percent because part of the work is spent on overcoming friction and other resistance.
Example: inclined plane
A
Got it.
= m·g·h (load lifted to height h)
A
morning
= F°l (trailed along l inclined length)
η = mgh / (F·l) · 100%
📊
Scratch (Visualization)
IV-038 · Animation of rise + energy balance + indicator of the AAC
h:
1
m
l:
5
m
m:
10
kg
F:
30
H
C
What needs to be understood
Outcome 1
Explain the physical meaning of "Golden Rules of Mechanics" through a model, not just a formula.
Outcome 2
Distinguish and correctly use terms: golden mechanics rule, useful work, hard work.
Outcome 3
Indicate the conditions for the applicability of the law, verify units and limit cases.
T
Terms of the topic
The definition should indicate the physical meaning, not a substitute for a domestic synonym.
The golden rule of mechanics
In an ideal simple mechanism, the gain in power is offset by a long-distance loser, so the job does not win.
Useful work
Part of the work spent corresponding to the mechanism &apos; s target.
Work done
Full operation of external forces or energy sources, including useful work and losses.
SAP
Ratio of useful energy or work to that spent; unlimited, usually expressed as a percentage.
F
Origin and conclusion of the formulas
The fundamental law cannot be "proven" by algebras: for each record, it is stated whether it is a definition, an experimental law, or a model effect.
η
=
A
пол
A
затр
⋅
100
%
\eta=\frac{A_{\text{пол}}}{A_{\text{затр}}}\cdot100\%
η
=
A
morning
​
A
Gender
​
​
⋅
100%
definition
The mechanism's efficiency.
The following is an indication of the definition, experience or law from which this entry arises and where it is applicable.
0
≤
A
пол
≤
A
затр
0\le A_{\text{пол}}\le A_{\text{затр}}
0
≤
A
Gender
​
≤
A
morning
​
Useful work is part of the work done, and the rest of the energy is spent on friction and other losses.
A
пол
A
затр
\frac{A_{\text{пол}}}{A_{\text{затр}}}
A
morning
​
A
Gender
​
​
The AAC is introduced as an unlimited share of the work done and has produced a useful result.
η
=
A
пол
A
затр
⋅
100
%
\eta=\frac{A_{\text{пол}}}{A_{\text{затр}}}\cdot100\%
η
=
A
morning
​
A
Gender
​
​
⋅
100%
This percentage is expressed in percentage terms by 100%.
Conditions:
The two works relate to the same process and are measured in the same units; Azatra > 0, the mechanism boundary is determined in advance.
Monitoring:
The dimensions of both parts shall coincide; the result shall be checked for sign, order and limit case.
!
Model boundaries and typical errors
Error: Forget model condition
You can't move the formula to any situation just because it's a coincidence of letters. The key condition of this topic is that free cheese is only in a mousetrap. No mechanism wins a job: how many times you win, you lose so much in distance.
How to Check the Mind
The formula is only applicable after selecting the system and assumptions. Then check the unit, vector direction and result behaviour at zero or very large parameter.
Σ
Conclusion on the topic
The golden rule of mechanics
Free cheese only happens in a mousetrap. No mechanism wins a job: how many times we win, we lose so much at a distance.
Free cheese only happens in a mousetrap. No mechanism wins a job: how many times we win, we lose so much at a distance.
The formula is applicable only after the selection of the system and assumptions.
Any numerical result shall be accompanied by a unit, a sign and an explanation of its physical meaning.
The content is consistent with the FRP on Physics of the OS/OSS 2025 and the subject matter of the current lines of the PNP: I. M. Peryškin and co-authors (7–9), G. J. Mäkishev and coauthors (10–11), and with the lines "Engineers of the Future" and V. A. Kasyanov. The original texts are not reproduced, the text of the textbooks is not reproduced.