Newton's Laws

Содержание и основные понятия

The dynamics link the acceleration of the body to the forces acting on it. Newton's laws apply in inertial systems the countdown and treat each body separately.
GEF · Grade 9
PIF · Baseline
Interactive model
inertia
inertial system
equal effect
Mass
Newton laws
01
The physical picture
What happens and what boundaries the model has.
Main message
The dynamics link the acceleration of the body to the forces acting on it. Newton's laws apply in inertial systems the countdown and treat each body separately.
If the equal is zero, the body speed is constant.
The acceleration is co-directed in equal and inversely proportional to the mass.
The forces of action and opposition are attached to different bodies, so they do not compensate each other.
How to reason
First, name the system and the interaction, then select the values, and only then write down the law. The formula works within the model's assumptions.
02
Laws and values
Symbols should be read as a relationship of values, not as a recipe for substitution.
∑
F
⃗
=
m
a
⃗
\sum\vec F=m\vec a
∑
F
=
m
a
Newton's Second Law
F
⃗
12
=
−
F
⃗
21
\vec F_{12}=-\vec F_{21}
F
12
​
=
−
F
21
​
Newton's Third Law
Review of the situation
Double the mass of the trolley with the same acceleration requires a double equal force.
04
Links and application
In the real world
Double the mass of the trolley with the same acceleration requires a double equal force.
Model verification
Compare the prediction with observation, evaluate the units, the order of magnitude and the influence of the factors not taken into account. Disparity does not always mean an error of law: often idealization is no longer sufficient.
C
What needs to be understood
Outcome 1
Explain the physical meaning of the topic "Newton Law" through a model, not just a formula.
Outcome 2
Distinguish and correctly use terms: inertia, inertia, equidistant system.
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.
inertia
Body property to maintain velocity at zero equal force.
inertial system
The counting system in which the free body is resting or moving evenly and flatly.
equal effect
The vector sum of all the forces attached to the body selected.
Mass
Body inertia measure and source of gravitational interaction.
Newton laws
Three basic laws of classical mechanics linking inertial systems, force and body movement.
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.
∑
F
⃗
=
m
a
⃗
\sum\vec F=m\vec a
∑
F
=
m
a
Postulate or Model
The second law of Newton.
The following is an indication of the definition, experience or law from which this entry arises and where it is applicable.
a
⃗
∥
∑
F
⃗
\vec a\parallel\sum\vec F
a
∥
∑
F
Experience in inertial systems shows that acceleration is directed as an equal force applied.
a
∝
F
рез
,
a
∝
1
m
a\propto F_{\mathrm{рез}},\quad a\propto\frac{1}{m}
a
∝
F
res.
​
,
a
∝
m
1
​
Experimentalally, acceleration is directly dependent on equidistant and reverse inert mass.
∑
F
⃗
=
m
a
⃗
\sum\vec F=m\vec a
∑
F
=
m
a
These results are accepted as Newton's second law, not the means of the Newton mechanics themselves.
Conditions:
Inertial counting system; body mass constant, speed much less than light speed, all external forces accounted for.
Monitoring:
The dimensions of both parts shall coincide; the result shall be checked for sign, order and limit case.
F
⃗
12
=
−
F
⃗
21
\vec F_{12}=-\vec F_{21}
F
12
​
=
−
F
21
​
Postulate or Model
The third law of Newton.
The following is an indication of the definition, experience or law from which this entry arises and where it is applicable.
F
⃗
12
действует на тело
2
,
F
⃗
21
действует на тело
1
\vec F_{12}\text{ действует на тело }2,\quad \vec F_{21}\text{ действует на тело }1
F
12
​
in force
as at
body
2
,
F
21
​
in force
as at
body
1
When interacting, they select a pair of forces that are applied to different bodies.
∣
F
⃗
12
∣
=
∣
F
⃗
21
∣
|\vec F_{12}|=|\vec F_{21}|
∣
F
12
​
∣
=
∣
F
21
​
∣
The mechanical experiments establish the equality of the modules of these forces while simultaneously interacting.
F
⃗
12
=
−
F
⃗
21
\vec F_{12}=-\vec F_{21}
F
12
​
=
−
F
21
​
The opposite of directions is recorded minus; equality is the postulate of the Newton model, not the result of equilibrium.
Conditions:
Classic mechanics and body mating; forces are applied to different bodies and therefore do not add up as forces on one body.
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
The key condition of this subject is that if the equal is zero, the body speed is constant.
How to Check the Mind
The acceleration is co-directed to equal and inversely proportional to the mass. Then check the units, vector direction and result behaviour at zero or very large parameter.
Σ
Conclusion on the topic
Newton's Laws
The dynamics link the acceleration of the body to the forces acting on it. Newton's laws apply in inertial systems the countdown and treat each body separately.
If the equal is zero, the body speed is constant.
The acceleration is co-directed in equal and inversely proportional to the mass.
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.