Work and capacity

Содержание и основные понятия

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Alterna · physics · 4.1
Work and capacity
Mechanical work, power, units
What's work in physics? It's not just work, it's a work of power on the road, and power is the speed of work. Why is a car more powerful than a horse?
GEF · Grade 7
PIF · Baseline
01
Mechanical work
When do we say work is done?
Mechanical work
Mechanical work
is the physical value equal to the work of force on the path that the body has travelled under the influence of that force.
A = F · s
where F is force (N), s is the path (m). Unit:
Joul (J)
1 J = 1 N · 1 m.
When isn't the job done?
The force is active but the body is not moving (s = 0) A = 0
Body is moving on inertia (F = 0) A = 0
The force is perpendicular to the movement (α = 90°) A = 0
Common formula with angle:
A = F · s · cos(α)
💼
Mechanically operated calculator
IV-032 · A = F·s·cos(α)
F:
10
H
s:
5
m
Angle α:
0
°
02
Power
If you work faster, you're more powerful.
Power
Power
is a physical value equal to the work in which it was done.
N = A / t
Unit:
watt (W)
1 W = 1 J/s.
Other units: 1 kW = 1000W, 1 MW = 106 W, 1 hp (horse force) ~ 735 W.
It's curious, the work of the human body
A man in a calm state develops ~75 W. With short-term loads (run, climbing stairs) up to 500–800 W. The horse averages 735 W (horse force).
⚡
Power — A Comparison
IV-033 · N = A/t, who will lift the load faster?
Work A:
1000
J
Time t:
10
c
C
What needs to be understood
Outcome 1
Explain the physical meaning of the topic "Work and power" through the model, not just the formula.
Outcome 2
To distinguish and correctly use terms: mechanical work, power, joule.
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.
mechanical work
The scalar measure of energy transmission by force when moving the point of its application.
Power
Work or energy transferred per unit of time.
Joul
Unit of power and work of SI equal to the force of 1 N at 1 m along the force.
watt
The unit of power of the SI is equal to one Joule per second.
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.
A
=
F
s
cos
⁡
α
A=Fs\cos\alpha
A
=
F
s
cos
α
definition
Mechanical work.
The following is an indication of the definition, experience or law from which this entry arises and where it is applicable.
F
∥
=
F
cos
⁡
α
F_{\parallel}=F\cos\alpha
F
∥
​
=
F
cos
α
Out of the constant force, only the projection to the direction of travel contributes to the movement.
A
=
F
∥
s
A=F_{\parallel}s
A
=
F
∥
​
s
The constant force is introduced as a product of its longitudinal component to move the application point.
A
=
F
s
cos
⁡
α
A=Fs\cos\alpha
A
=
F
s
cos
α
Cosine α distinguishes positive, zero and negative work.
Conditions:
The force is constant in the module and direction, the movement is straight; α is the angle between the force and the movement.
Monitoring:
The dimensions of both parts shall coincide; the result shall be checked for sign, order and limit case.
N
=
A
t
N=\frac{A}{t}
N
=
t
A
​
definition
Power.
The following is an indication of the definition, experience or law from which this entry arises and where it is applicable.
N
ср
=
совершённая работа
время
N_{\text{ср}}=\frac{\text{совершённая работа}}{\text{время}}
N
cf
​
=
time
done by
work
​
The average mechanical capacity is introduced as a work done per unit of time.
N
=
A
t
N=\frac{A}{t}
N
=
t
A
​
If work A is performed over interval t, their ratio shows the average speed of work.
Conditions:
t > 0; at variable force or speed, the formula sets the average power over the chosen interval.
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 the letters match. The key condition of this subject is that the force is active but the body isn't moving (s = 0) A = 0
How to Check the Mind
The body is moving on inertia (F = 0) A = 0 then check the units, direction of vectors and behaviour of the result at zero or very large parameter.
Σ
Conclusion on the topic
Work and capacity
What's work in physics? It's not just work, it's a work of power on the road, and power is the speed of work. Why is a car more powerful than a horse?
The force is active but the body is not moving (s = 0) A = 0
Body is moving on inertia (F = 0) A = 0
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.