Mechanical movement

Содержание и основные понятия

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Alterna · physics · 2.1
Mechanical movement
Movement, speed, acceleration, graphs
The world isn't standing still. Machines, planets, molecules are moving. But what does "move" mean? How do you measure speed? And why is it that even movement in nature is almost non-existent?
GEF · Grade 7
PIF · Baseline
01
Mechanical movement
What does "body moves" mean?
Definition
Mechanical movement
is a change in the position of the body in space relative to other bodies over time.
Movement
concerning
: passenger on the driving bus resting relative to the bus but moving relatively on the road.
Account Body
- body to which movement is considered
Reporting system
- counting body + coordinate system + clock
Trajectory
- Line through which the body moves
Path
(s) is the length of the trajectory measured in metres (m)
Displacement
- directed from the beginning to the end
Units of the road
1 km = 1000 m 1 m = 100 cm = 1,000 mm 1 cm = 10 mm
02
Equitable and uneven movement
Two types of traffic: when speed is constant and when speed changes.
Equitable movement
Equitable movement
— The body goes on the same path for any equal time interval.
An example is a car on a cruise-control on a straight path — 20 m in every second.
Uneven traffic
Uneven traffic
— The body for equal periods of time travels in different ways.
Most of the movements in nature are uneven. The car touches, slows down, accelerates.
🚗
Animation of motion with speed vector
IV-010 · Trace trajectory + growing speed vector + track markings
Type:
v₀:
3
m/s
a:
0.5
m/s2
Press "Start"
🎯
Movement of body at an angle
IV-010B · NEW · Parabolic trajectory · Change angle and speed, watch flight
Angle α:
45
°
Speed v0:
30
m/s
03
Speed, speed units
How fast does the body move?
Equivalent speed
Speed
is a physical value equal to the distance from the time that this journey is over.
v = s / t
Unit of measure:
meter per second (m/s)
.
Other units: km/h, see/s.
Subtitles:
1 km/h = 1000/3600 m/s E 0.278 m/sec
Return: 1 m/s = 3.6 km/h
Example
The vehicle drove 90 km in 1.5 hours. Speed: v = 90/1.5 = 60 km/h = 60/3.6 ER 16.7 m/s.
04
Calculation of the path and time
From the formula v = s/t is obtained s = v·t and t = s /v.
Three formulas
v = s/t
→
s = v · t
→
t = s/v
Knowing two dimensions, you can always find a third.
📦
Speed, track and time calculator
IV-012 · Enter two values — receive the third
Speed v (m/s):
Path s (m):
Time t (s):
Fill in two fields
📊
S(t) and v(t).
IV-011 · Draw graphs according to parameters
v0 (m/s):
5
a (m/s2)
0.0
t
max
(c):
10
05
Acceleration
How is uneven movement characterized?
Acceleration
Acceleration
is a physical value equal to the rate change relative to the time that the change occurred.
a = (v − v₀) / t
Unit:
meter per second squared (m/s2)
.
In equidistant motion:
v = v₀ + a·t
s = v₀·t + a·t²/2
🚀
Acceleration - Slider Experiment
IV-013 · Equated speed + graph v(t)
v₀:
0
m/s
a:
2.0
m/s2
C
What needs to be understood
Outcome 1
Explain the physical meaning of the topic "Mechanical movement" through the model, not just through the formula.
Outcome 2
Distinguish and correctly use terms: counting system, trajectory, path.
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.
Reporting system
The countdown body, the related coordinate system and the time measurement method.
trajectory
A line that is described by the moving material point in the selected accounting system.
route
A scalar value equal to the length of the trajectory section.
speed
A vector value showing the speed and direction of the change in position.
acceleration
Vector value of speed change per unit time.
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.
v
=
s
t
v=\frac{s}{t}
v
=
t
s
​
definition
The speed of steady motion.
The following is an indication of the definition, experience or law from which this entry arises and where it is applicable.
v
ср
=
s
t
v_{\text{ср}}=\frac{s}{t}
v
cf
​
=
t
s
​
The average travel speed is introduced as a journey per unit of time.
v
=
c
o
n
s
t
v=\mathrm{const}
v
=
const
In uniform traffic, the same paths run over the same intervals, so the average speed at any section coincides with the constant speed.
v
=
s
t
v=\frac{s}{t}
v
=
t
s
​
So the determination of average speed becomes the formula of even speed.
Conditions:
Equivalent movement, s is the length of the path over time t > 0; directional movement requires vector speed and movement.
Monitoring:
The dimensions of both parts shall coincide; the result shall be checked for sign, order and limit case.
s
=
v
t
s=vt
s
=
v
t
model effect
The way.
The following is an indication of the definition, experience or law from which this entry arises and where it is applicable.
v
=
s
t
v=\frac{s}{t}
v
=
t
s
​
For even traffic, speed is equal to the path to time.
v
t
=
s
vt=s
v
t
=
s
The multiplication of both parts of the equality by the length of traffic t expresses the path travelled.
s
=
v
t
s=vt
s
=
v
t
The path grows linearly over time at constant speed.
Conditions:
V speed is constant and non-negative, t ≥ 0; the formula gives the path, not the coordinates, in the arbitrary direction of traffic.
Monitoring:
The dimensions of both parts shall coincide; the result shall be checked for sign, order and limit case.
a
=
Δ
v
Δ
t
a=\frac{\Delta v}{\Delta t}
a
=
Δ
t
Δ
v
​
definition
Acceleration.
The following is an indication of the definition, experience or law from which this entry arises and where it is applicable.
Δ
v
=
v
2
−
v
1
\Delta v=v_2-v_1
Δ
v
=
v
2
​
−
v
1
​
First they find a change in speed over the chosen time interval.
a
ср
=
Δ
v
Δ
t
a_{\text{ср}}=\frac{\Delta v}{\Delta t}
a
cf
​
=
Δ
t
Δ
v
​
The average acceleration shall be applied as a change in speed per unit time.
a
=
Δ
v
Δ
t
a=\frac{\Delta v}{\Delta t}
a
=
Δ
t
Δ
v
​
With constant acceleration, this ratio is the same at all intervals and is equal to acceleration.
Conditions:
Direct motion in the scalar record and Δt > 0; vectors Δv and a are used for crooked motion.
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 transfer the formula to any situation just because it's a coincidence of letters.
How to Check the Mind
The countdown system is the countdown body + coordinate system + clock then check the units, vector direction, and result behaviour at zero or very large parameter.
Σ
Conclusion on the topic
Mechanical movement
The world isn't standing still. Machines, planets, molecules are moving. But what does "move" mean? How do you measure speed? And why is it that even movement in nature is almost non-existent?
The countdown body is the bo