Download Kinematics - Gymnázium Slovanské náměstí

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Gymnázium, Brno, Slovanské náměstí 7
III/2 – Inovace a zkvalitnění výuky prostřednictvím ICT
Inovace výuky na GSN prostřednictvím ICT
CZ.1.07/1.5.00/34.0940
RNDr. Bc. Miroslav Hruška
Dynamics of particles (dynamika hmotných bodů)
Newton’s first law of motion
VY_32_INOVACE_FY.3.02
27. 9. 2013
Žáci středních škol s CLIL výukou fyziky v angličtině
Dynamics, Newton’s first law of motion, force, inertial frame
of reference, non-inertial frame of reference, inertia,
friction, air resistance
Prezentace slouží k uvedení do problematiky prvního
Newtonova pohybového zákona. Je vhodné ji použít při
probírání nového učiva.
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Dynamics of particles
2. Newton’s first law of motion
Newton’s laws of motion
In 1687 Isaac Newton published his
three laws of motion (pohybové zákony)
 Newton’s laws are describing the
relationship between motion and forces
 However, Newton found out that
in some frames of reference the laws
are valid, and in some not…
st
 1 Newton’s law belongs to Galileo!

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Inertial and non-inertial frames

Frames of reference where Newton’s
laws are valid are called inertial, while
the others are called non-inertial

The Earth, as a frame of reference, is
almost inertial (slight differences can
appear, and can be very important in
some cases)

http://www.youtube.com/watch?v=Q0Wz5P0JdeU 6:33

http://www.khanacademy.org/science/physics/forces-newtons-laws/newtons-laws-of-motion/v/newton-s-1st-law-of-motion 5:26
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Newton’s first law of motion
= law of inertia (zákon setrvačnosti)
 “A body is at rest or in uniform
rectilinear motion unless made to
change its state by external forces.”
 „Každé těleso setrvává (persists) v klidu
nebo v rovnoměrném přímočarém
pohybu, pokud není nuceno vnějšími
silami tento svůj stav změnit.“

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Non-inertial frames of reference
A train speeding up
 A tram slowing down
 A car turning a curve
…
 Inertia is a property of matter by which

it remains in a state of rest or continues
moving uniformly in a straight line unless
acted on by an external force
Zdroj: archiv autora
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Revision





Who formulated the laws of motion?
How many are the laws of motion?
What does it mean when a frame of
reference is inertial?
What do you know about inertiality of
a frame of reference connected with
Earth?
Give examples of non-inertial frames
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Revision – answers
Isaac Newton
 Three
 Newton’s laws are valid there
 Earth’s frame of reference is almost
inertial
 A vehicle speeding up, slowing down,
turning

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Inertial frames of reference
If there is a frame of reference at rest
or in uniform rectilinear motion
relative (with respect) to an inertial frame
of reference, then it is inertial too!
 So a train going at constant velocity
(at constant speed on a straight track)
can be taken as an inertial frame of
reference

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Friction and air resistance
Sometimes we think an object should
keep moving uniformly, but it stops…
 On the other hand, sometimes we
expect a uniformly accelerated motion,
and we are surprised that the motion
becomes uniform… Give an example
 We must take into account friction and
air resistance!

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No forces vs balanced forces
If there are more forces acting on an
object, and they are balanced
(v rovnováze), i.e. their resultant is a
zero vector, then it is the same situation
as if there are no forces at all
 However, is it true
when we talk about
deformation effect?

Zdroj: archiv autora
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Complete with proper words
A body is at …… or in uniform rectilinear
motion unless …… to change its …… by
external ……
 …… is a property of matter by which it
…… in a state of rest or continues
moving uniformly in a …… line, unless
acted on by an …… force


http://www.youtube.com/watch?v=M_8w-dD4RBE 49 min Newton’s laws
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That is all for now
Thank you for your attention

Materiál je určen pro bezplatné používání pro potřeby výuky
a vzdělávání na všech typech škol a školských zařízeních.
Jakékoliv další využití podléhá autorskému zákonu.
Zdroje:


Bednařík, M., Široká, M. Fyzika pro gymnázia, Mechanika.
Dotisk 3. vyd. Praha: Prometheus, 2004. 288 s. ISBN 807196-176-0
Hornby, A. S. Oxford Advanced Learner’s Dictionary of
Current English. 5. vyd. Oxford: Oxford University Press,
1995. 1428 s. ISBN 0-19-431423-5
Autor nezaručuje funkčnost webových odkazů!
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