1 Škola: Gymnázium, Brno, Slovanské náměstí 7 Šablona: III/2 – Inovace a zkvalitnění výuky prostřednictvím ICT Název projektu: Inovace výuky na GSN prostřednictvím ICT Číslo projektu: CZ.1.07/1.5.00/ Autor: RNDr. Bc. Miroslav Hruška Tematická oblast: Dynamics of particles (dynamika hmotných bodů) Název DUMu: Newton’s first law of motion Kód: VY_32_INOVACE_FY.3.02 Datum: Cílová skupina: Žáci středních škol s CLIL výukou fyziky v angličtině Klíčová slova:Dynamics, Newton’s first law of motion, force, inertial frame of reference, non-inertial frame of reference, inertia, friction, air resistance Anotace: Prezentace slouží k uvedení do problematiky prvního Newtonova pohybového zákona. Je vhodné ji použít při probírání nového učiva.

Dynamics of particles 2. Newton’s first law of motion

3 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…  1 st Newton’s law belongs to Galileo!

4  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)  6:33  5:26 Inertial and non-inertial frames

5  = 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.“ Newton’s first law of motion

Zdroj: archiv autora6 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

7  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 Revision

8 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

9  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 Inertial frames of reference

10  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! Friction and air resistance

Zdroj: archiv autora11  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? No forces vs balanced forces

12  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  49 min Newton’s laws Complete with proper words

That is all for now Thank you for your attention

14  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, s. ISBN  Hornby, A. S. Oxford Advanced Learner’s Dictionary of Current English. 5. vyd. Oxford: Oxford University Press, s. ISBN Autor nezaručuje funkčnost webových odkazů!