Simple mechanisms

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Alterna · physics · 4.2
Simple mechanisms
Rush, moment of strength, blocks
The scissors, the pins, the weight levers are all simple mechanisms. They don't create energy, but they do win. How does the lever rule work?
GEF · Grade 7
PIF · Baseline
01
Simple mechanisms
Tools that facilitate work.
Simple mechanisms
Simple mechanisms
- power conversion devices: win the force or change the direction of the force.
Ginger
- A solid body spinning around the point of support
Block
- A wheel with a yellow rope on it.
Sloping plane
- to lift cargo to altitude
Clay.
- separates or secures
Blade
- an inclined plane folded into a spiral
02
The power balance.
Leverage rule: F1l1 = F2l2.
Ginger
Ginger
is a solid body that can rotate around a fixed axis (hold points).
The Shoulder of Force
is the shortest distance from the axis of rotation to the force line.
The rule of lever equilibrium
F₁ · l₁ = F₂ · l₂
The beam is in equilibrium if the work of strength on the shoulder on one side is equal to the work on the arm on the other.
⚖
Rush — Balance With Animation
IV-034 · F1l1 = F2l2 · Rychag is smooth and comes to equilibrium
F₁:
10
H
l₁:
3
I'm sorry, I've got to go.
F₂:
15
H
l₂:
2
I'm sorry, I've got to go.
03
Moment of strength
Rule of events: sum of moments by clock = sum versus clock.
Moment of strength
Moment of strength
- it's a work of strength on the shoulder.
M = F · l
Unit: Nm (newton-metre).
Rule of moments
The market is in equilibrium, if the sum of the moments of the clockwise forces is equal to the amount of the times of the counterclockwise forces.
ΣM
One hour.
= ΣM
against one hour.
↻
Moment of force - rule (visualization)
IV-035 · Calculator + Animated torque scale
F₁:
10
H
l₁:
4
m
F₂:
20
H
l₂:
2
m
04
Blocks
Fixed and mobile unit.
Fixed block
Fixed block
- Axis fixed, block not moved, doesn't win, but
changes direction
Power.
F = P (no win)
Mobile unit
Mobile unit
- Axe moves with cargo.
Double wins
.
F = P/2 (but the rope has to be pulled twice as much)
⚙
Blocks — Animation of the Cargo
IV-036 · Winning in force · Press "Push" to lift the cargo
Type:
Mass of load m:
10
kg
05
Rings in technology, welfare and nature
Where do the levers meet?
♪ Technology ♪ ♪ Rock ♪
Scissors
- Two levers with a common axis, long handles, short blades, win-win.
Scratches
- even more wins.
Rush scales
- Equivalent leverage.
Driving of the vehicle
- lever (driver + column).
Rings in nature
Human Hand
- lever: elbow = support, bicep = force, hand load = load.
Jaws
- the lever for biting.
Animal Legs
- running levers and jumps.
C
What needs to be understood
Outcome 1
Explain the physical meaning of the topic "Simple mechanisms" through the model, not just through the formula.
Outcome 2
Clear and correct use of terms: lever, shoulder, moment of strength.
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.
lever
A solid body capable of spinning around a support and used to transform power.
Shoulder
The maximum distance from the axis of rotation to the force line.
force moment
Measure of rotation of force relative to the axis or point.
Unit
A simple device with a galley for a thread that changes the direction of power or gives effect.
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.
M
=
F
l
M=Fl
M
=
Fl
definition
A moment of strength.
The following is an indication of the definition, experience or law from which this entry arises and where it is applicable.
l
=
расстояние от оси до линии действия силы
l=\text{расстояние от оси до линии действия силы}
l
=
distance
from
axles
up to
lines
Action
force
The shoulder of force is defined as the shortest, i.e. perpendicular, distance to its line of action.
M
=
F
l
M=Fl
M
=
Fl
The moment of force is inserted as a work of a force module on the shoulder to describe its rotating effect.
Conditions:
A flat task in which the axis is perpendicular to the force plane; F is a force module and l is perpendicular the distance from the point of intersection of the axis with that plane to the line of force. In general, the projection of the vector r × F on the axis shall be used.
Monitoring:
The dimensions of both parts shall coincide; the result shall be checked for sign, order and limit case.
F
1
l
1
=
F
2
l
2
F_1l_1=F_2l_2
F
1
​
l
1
​
=
F
2
​
l
2
​
model effect
The balance of the lever.
The following is an indication of the definition, experience or law from which this entry arises and where it is applicable.
∑
M
=
0
\sum M=0
∑
M
=
0
In order to balance the lever, the sum of the force moments relative to the support shall be zero.
M
1
=
F
1
l
1
,
M
2
=
F
2
l
2
M_1=F_1l_1,\qquad M_2=F_2l_2
M
1
​
=
F
1
​
l
1
​
,
M
2
​
=
F
2
​
l
2
​
The forces on different sides of the support leg create opposite points of direction.
M
1
=
M
2
⇒
F
1
l
1
=
F
2
l
2
M_1=M_2\Rightarrow F_1l_1=F_2l_2
M
1
​
=
M
2
​
⇒
F
1
​
l
1
​
=
F
2
​
l
2
​
Equity requires equality of rotation modules.
Conditions:
Rigid non-weightable lever in rest; only two non-zero opposite moments of F1l1 and F2l2 operate relative to the support. If the weight of the lever, friction or other forces is significant, the full equation \M = 0 with their moments shall be applied instead of the two-member equation.
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 the rock is a solid body that rotates around the point of support.
How to Check the Mind
The block is a yellow wheel that passes a rope and then check the units, vector direction, and result behaviour at zero or very large parameter.
Σ
Conclusion on the topic
Simple mechanisms
The scissors, the pins, the weight levers are all simple mechanisms. They don't create energy, but they do win. How does the lever rule work?
Ring is a solid body that rotates around the point of support.
The block is a yellow wheel that carries a rope.
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.