Škola: Gymnázium, Brno, Slovanské náměstí 7

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.1.07/1.5.00/34.0940 Autor: RNDr. Bc. Miroslav Hruška Tematická oblast: Gravitational field and motion of bodies (gravitační pole a pohyb těles) Název DUMu: Hydrostatics – revision Kód: VY_32_INOVACE_FY.4.17 Datum: 22. 4. 2014 Cílová skupina: Žáci středních škol s CLIL výukou fyziky v angličtině Klíčová slova: Hydrostatics, hydrostatic pressure, Pascal’s law, Archimedes’ principle Anotace: Prezentace procvičuje principy Pascalova a Archimedova zákona

2. Gravitational field and motion of bodies 17. Hydrostatics – revision

3. Hydrostatics Which law deals with pressure, and which with force?

4. Fill in the gaps I • The cause of the ……………. in a fluid can be: • an ………………force acting on the fluid • the forces of ………… acting on individual …………….. of the fluid • The pressure ………… by an …………..force acting on a liquid in a closed ……………… is at all ………. of the liquid the same

5. Fill in the gaps I – solution • The cause of the pressure in a fluid can be: • an external force acting on the fluid • the forces of gravity acting on individual particles of the fluid • The pressure caused by an external force acting on a liquid in a closed container is at all points of the liquid the same

6. Exercise I • A force of 10 N acts on the small piston of a hydraulic device of radius 2 cm. The large piston has got a radius of 20 cm. Find the magnitude of the force acting on the large piston? • F1 = 10 N, r1 = 2 cm, r2 = 20 cm • F2 = ?

7. Solution I • The area of the small piston is S1 = π × 22 cm2 • The area of the large piston is S2 = π × 202 cm2 • The force acting on the large piston is N

8. Fill in the gaps II • We refer to the …………… caused by the forces of …………… acting on individual particles of a liquid as the ………………pressure • Any object ………………. in a liquid is …………… up by a force equal to the ………… of the liquid …………… by the object

9. Fill in the gaps II – solution • We refer to the pressure caused by the forces of gravity acting on individual particles of a liquid as the hydrostatic pressure • Any object immersed in a liquid is buoyed up by a force equal to the weight of the liquiddisplaced by the object

10. Exercise II • Find the hydrostatic pressure in water at a depth of 5 m. • h = 5 m, ρ = 1000 kg/m3, g = 10 m/s • ph = ? • ph = hρg =5 × 1000 × 10 Pa = 50 kPa The hydrostatic pressure is 50 kPa.

11. Exercise III • Find the net force actingon an iron cube of volume 100 cm3 completely immersed in water (ρt = 7860 kg/m3). • The buoyant force Fvz • The force of gravity FG

12. Solution III Since ρT > ρk,F = FG– Fvz= 7.86 N – 1.00 N = 6.86 N • V = 100 cm3 = 0.0001 m3 • ρT = 7860 kg/m3 • g = 10 m/s2 • ρk = 1000 kg/m3 • The buoyant force Fvz • The force of gravity FG

13. 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, 2004. 288 s. ISBN 80-7196-176-0 • 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