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: Inertial frames of reference. Galilei’s principle of relativity Kód: VY_32_INOVACE_FY.3.09 Datum: Cílová skupina: Žáci středních škol s CLIL výukou fyziky v angličtině Klíčová slova:Inertial frame of reference, principle of relativity Anotace: Prezentace slouží k vysvětlení Galileiho principu relativity. Je vhodné ji použít při probírání nového učiva. Na začátku se opakuje předchozí učivo.

Dynamics of particles 9. Inertial frames of reference. Galilei’s principle of relativity

3  When do we use the term of centripetal force?  Is centripetal force a type of force?  What is the formula for centripetal force?  What direction does centripetal force have?  Give two examples of centripetal force Revision I

4 Revision I – answers  When a particle moves uniformly round a circle  No, it is a name for a particular net force   It points towards the centre of the circular path  Gravitational force, static friction, …

5  Describe how a centripetal force arises at a merry-go-round Centripetal force

6 Exercise  A 1-tonne car is turning in a curve of a radius of 90 m with a constant speed of 90 km/h. Find the centripetal force.  m = 1000 kg r = 90 m  v = 25 m/s  F d = ?  F d = mv 2 ÷ r = 1000 × 25 2 ÷ 90 = 6900 N  The centripetal force is 6.9 kN.

7  Why do we say motion is relative?  What object is the most common frame of reference connected with?  What does a reference frame consist of?  What does it mean when a frame of reference is inertial?  What do you know about inertiality of a reference frame connected with Earth? Revision II

8 Revision II – answers  It depends on (relates to) an other object  The Earth (its surface)  Object of reference and coordinate system  Newton’s laws are valid there  Earth’s frame of reference is almost inertial

9  Let’s imagine an astronaut travelling inside a windowless spaceship, moving away from the Sun at constant velocity  According to Galilei’s principle of relativity ( principu relativity ) there are no mechanical experiments that can be made inside the rocket that will tell the astronaut that the rocket is moving Galilei’s principle of relativity

10  Galilei’s ( Galilean ) principle of relativity is a principle of the physical equality of inertial frames of reference in classical mechanics, which is manifested in the fact that the laws of mechanics are identical in all such reference frames Galilei’s principle of relativity

11  It is impossible to determine by any mechanical experiment conducted in any inertial frame of reference whether the given frame of reference is at rest or moving uniformly and rectilinearly Galilei’s principle of relativity

That is all for now Thank you for your attention

13  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