HELP

1 Match the beginning of each sentence with the correct ending. Write out each complete sentence.

Beginnings / Endings
A Communication satellites are used to / 1 are called navigation satellites.
B Observation satellites can / 2 send telephone messages around the world.
C The type of satellites used by ships to find their position on the Earth / 3 are called space stations.
D Exploration satellites can / 4 take detailed photographs of the Earth.
E The type of satellites where astronauts can live and work in space / 5 take very clear pictures of the planets.

2 a Give the name of one natural satellite of the Earth.

b What keeps this natural satellite from flying off into outer space?

c Give one difference between this natural satellite and the Earth.

CORE

3  Telstar was the first artificial satellite to be put into Earth orbit. It could be seen crossing the night sky, from north to south. It took about 15 minutes to cross from the northern horizon to the southern horizon.

a i What type of orbit was being used by Telstar?

ii Explain how its position in the night sky would have been different, if it had been in the other type of orbit.

b i Telstar could be seen as a bright object moving across the night sky on a clear night. It had no lights. Explain why it could be seen so clearly.

ii Telstar also crossed the sky during the day but could not be seen. Explain why not.

c i Telstar was used to carry live television pictures across the globe. Times were booked in advance. Sometimes, if the programme overran, the pictures suddenly cut out. Explain why this happened.

ii What is the advantage of modern communication satellites, compared with those in orbits like Telstar?

d Which of the following satellites would normally be in geostationary orbits around the Earth?

A – exploration satellites B – navigation satellites

C – communication satellites D – the Moon

EXTENSION


4 Look at the diagram showing forces acting on the Moon as it orbits the Earth.

a What would happen to force A if the speed of the Moon decreased?

b If the speed of the Moon did decrease, what would happen to the Moon?

c Explain how forces A and B together are responsible for keeping the Moon in its orbit round the Earth.

d Explain why the Moon orbits the Earth, rather than having its own orbit around the Sun.

e When the Apollo missions went to the Moon their speed decreased as they moved away from the Earth and then increased as they approached closer to the Moon. Use your knowledge about gravitational attraction to explain why this happened.

© Harcourt Education Ltd 2004 Catalyst 3

This worksheet may have been altered from the original on the CD-ROM.