IGCSE+ASTRONOMY

IGCSE PHYSICS > FORCES AND MOTION =ASTRONOMY= [|SPACE SHUTTLE SLIDESHOW] (6 min) 1.30 recall that the moon orbits the earth and that some planets also have moons. [|FLASH MODEL OF THE SOLAR SYSTEM] - can you work out if it is to scale? 1.31 understand gravitational field strength, g, and recall that it is different on other planets and the moon from that on the earth. STORY OF SIR ISAAC NEWTON media type="custom" key="8705276" GRAVITATIONAL FORCE: A force between all masses which increases if the masses are large and decreases as they get further apart. GRAVITATIONAL FIELD STRENGTH: Different on the surface of each planet or satellite. [|IT IS EVEN DIFFERENT AT DIFFERENT PLACES ON EARTH] - click for article 1.32 explain that gravitational force – causes the planets to orbit the sun – causes the moon and artificial satellites to orbit the earth – causes comets to orbit the sun ACTIVITY See [|PHET simulation My Solar System] or on Studywiz (for fast download in school) to learn about orbits of planets, moons and comets.

1.33 use the relationship between orbital speed, orbital radius and time period ORBIT: A satellite will orbit around a larger body due to gravitational attraction. PRACTICE QUESTION Use the formula to calculate the speed of the Earth around the Sun if the orbital radius is 150 000 000 km.

1.34 describe how the orbit of a comet differs from that of a planet [|COMET NEWS STORY WITH PICS ON THE BBC]

THE ORBIT OF THE COMET: It is an eccentric ellipse; the speed increases when it is nearer to the Sun; it passes into and out of the planets' orbits.

1.35 recall that the solar system is part of the milky way galaxy – describe a galaxy as a large collection of billions of stars – state that the universe is a large collection of billions of galaxies.

[|ARTICLE ON BBC NEWS ABOUT THE MILKY WAY MAP] [|THE MILKY WAY MAP] - zoom in and in and in

THE UNIVERSE: contains 10^11 galaxies which contain 10^11 stars. Moons and satellites orbit planets which orbit stars. Comets orbit in an eccentric ellipse.