Force

Содержание и основные понятия

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Alterna · physics · 2.3
Force
Force of gravity, turgidity, weight, equidistant, dynamometer
Power is not just a word, it's a physical dimension that moves, pulls, pushes and stops everything around, and we take out seven kinds of power and learn how to measure it.
GEF · Grade 7
PIF · Baseline
01
Force
Power is a measure of body interaction.
What is power?
Force
- It's a physical dimension that characterizes the effect of one body on another.
vector
value: it has a module, direction and point of application.
Symbol:
F
III. Unit:
Newton (N)
.
1 N is the force that a body mass of 1 kg gives an acceleration of 1 m/s2.
Types of power in mechanics
Force of gravity
- The power the earth draws the body with
Force of turgidity
- force generated by deformation
Weight of body
- the force with which the body acts on the support or suspension
The strength of friction
- force generated by the movement of one body over the surface of the other
The strength of the support leg reaction
- the force with which the support acts on the body
02
Force of gravity.
The earth attracts all the bodies.
The Law of Global Burden
Force of gravity
It is the power with which the earth draws the body to itself.
F = m · g
where g = 9.8 N/kg is the acceleration of gravity.
The force of gravity is always directed
downwards
to the center of the Earth.
🦉
Free fall on planets
IV-016 · Animation of drop with real acceleration g
Planet:
Mass m:
10
kg
🎯
Galileo experience: Two balls falling simultaneously
IV-016B · Mass does not affect acceleration of gravity
Left mass:
1
kg
Mass of right:
50
kg
Galileo has proven that all bodies are falling at the same rate. Mass is not important. Press "Shoot the balls!"
03
The strength of turgidity.
Why is the spring stretching and compressing?
Force of turgidity
Force of turgidity
is the force that occurs in the body when it is deformed and seeks to restore it to its original state.
Hook's Law
F = k · Δl
where k is hardness (N/m), Δl is elongation (m).
The force of turgidity is directed
opposite
The deformation.
🔧
Hook's Law — A Spring Dynamometer
IV-017 · F = k ±l, interactive spring
Mass of load m:
1
kg
Rigid k:
50
N/m
04
Weight of body, relation to gravity
Weight is not mass! The difference is important.
Weight of body
Weight
is the force with which the body, because of its gravity to the Earth, acts on a horizontal support or vertical suspension.
Weight is marked
P
is measured in Newtons (N).
If the body is resting:
P = F
claim
= mg
Variance:
The gravity is attached to the body, the weight to the support.
It's curious.
At the orbital station, the cosmonauts are in no gravity: P = 0. It doesn't mean there's no gravity. It's just that the station and everything inside it is moving at the same speed without pushing each other.
05
Equal force
What if the body is affected by several forces?
Equitable
Equal force
- is a force that replaces several forces on the body.
The forces are directed in one direction:
R = F₁ + F₂
The forces are on opposite sides:
R = |F₁ − F₂|
The forces are at an angle, folding according to the rule of parallelogram.
➤
Consequence (equal)
IV-018 · Force vector calculator
F₁:
10
H
F₂:
5
H
Direction F2:
06
Dynamometer
A force measurement device.
Dynamometer
Dynamometer
Based on Guk's law, the spring is stretched proportionally to the force applied.
The scale is projected in Newtons. 1 kg mass extends the spring to 9.8 N E 10 N.
🔠
Dynamometer — Measurement of Force
IV-020 · Interactive instrument
Attach force F:
5
H
C
What needs to be understood
Outcome 1
Explain the physical meaning of the topic "The Force" through the model, not just the formula.
Outcome 2
To distinguish and correctly use terms: force, gravity, force of turgidity.
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.
force
Vectorial interacting measure causing acceleration or deformation of the body.
gravity
The power of gravitational gravity of the body of Earth or of another celestial body.
strength of turgidity
A force created by deformation and directed against a change of shape or body size.
weight
The power with which the body acts as a result of interaction on a support or suspension.
equal effect
The vector sum of all the forces attached to the body selected.
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
тяж
=
m
g
F_{\text{тяж}}=mg
F
claim
​
=
m
g
model effect
Force of gravity.
The following is an indication of the definition, experience or law from which this entry arises and where it is applicable.
F
⃗
=
m
a
⃗
\vec F=m\vec a
F
=
m
a
Newton's second law links equal force to acceleration.
a
⃗
=
g
⃗
\vec a=\vec g
a
=
g
​
In a freefall model near the surface of the Earth, the body is accelerated by the free fall.
F
⃗
тяж
=
m
g
⃗
\vec F_{\text{тяж}}=m\vec g
F
claim
​
=
m
g
​
If the resistance to air is ignored, this acceleration creates gravity.
Conditions:
Small heights near the surface of the celestial body, g are considered permanent; the mass of the body is small compared to that of the planet.
Monitoring:
The dimensions of both parts shall coincide; the result shall be checked for sign, order and limit case.
F
упр
=
k
Δ
l
F_{\text{упр}}=k\Delta l
F
Excuse me.
​
=
k
Δ
l
empirical law
The law of the goca.
The following is an indication of the definition, experience or law from which this entry arises and where it is applicable.
F
упр
∼
Δ
l
F_{\text{упр}}\sim\Delta l
F
Excuse me.
​
∼
Δ
l
The spring tests determine the proportionality of the small elongation force module.
k
=
F
упр
Δ
l
k=\frac{F_{\text{упр}}}{\Delta l}
k
=
Δ
l
F
Excuse me.
​
​
The proportionality factor k is called spring rigidity.
F
упр
=
k
Δ
l
F_{\text{упр}}=k\Delta l
F
Excuse me.
​
=
k
Δ
l
It's Guk's empirical law for modules; the direction of force is opposite to deformation.
Conditions:
The slight turgid deformation within the proportionality range, the spring temperature and properties are constant; the vectors need a negative sign.
Monitoring:
The dimensions of both parts shall coincide; the result shall be checked for sign, order and limit case.
R
⃗
=
∑
i
F
⃗
i
\vec R=\sum_i\vec F_i
R
=
i
∑
​
F
i
​
definition
Equivalent.
The following is an indication of the definition, experience or law from which this entry arises and where it is applicable.
F
⃗
1
,
F
⃗
2
,
…
\vec F_1,\vec F_2,\ldots
F
1
​
,
F
2
​
,
…
Each force has a module and a direction, so forces fold as vectors.
R
⃗
=
F
⃗
1
+
F
⃗
2
+
…
\vec R=\vec F_1+\vec F_2+\dots
R
=
F
1
​
+
F
2
​
+
…
The vector R is defined as the sum of all external forces. It fully describes their progressive effect on the material point or centre of the masses; for a long body, the total moment of the force must be taken into account separately