Q2.

The diagram, which is not to scale, shows two satellites, L and M, orbiting the Earth.

(a) Complete the following table. Each letter, L or M, may be used once, more than once or not at all.

Statement about the satellite	Letter for the satellite
It is used as a monitoring satellite.	M
It is a geostationary satellite.	L
It takes 24 hours to complete its orbit.	L

All correct - two correct

(2 marks)

(b) For a satellite to stay in a steady orbit around the Earth, what must be kept constant? (1 mark)

Speed.

You cannot have a mark for saying 'velocity' as the velocity is constantly changing as the direction constantly changes.

(c) Thousands of satellites are now in orbit around the Earth. A student used the Internet to collect information about some of them.

Name of satellite	Average distance from the centre of the Earth in kilometres	Speed in kilometres per second	Time taken to orbit the Earth
The Moon	391,400	1.01	28 days
GEO	42,200	3.07	1 day
Navstar	26,600	3.87	12 hours
Lageos	12,300	5.70	3.8 hours
HST	7,000	7.56	97 mins
ISS	6,700	7.68	92 mins

(i) The Moon takes a longer time than any of the other satellites to orbit the Earth. Give one other way in which the Moon is different from the other satellites in the table. (1 mark)

any one from:

• The Moon is a natural satellite
• The moon moves more slowly
• the Moon is the furthest (from the centre of the Earth)

(ii) What conclusion on the relationship between the average distance and speed can the student come to on the basis of this data? (1 mark)

As the (average) distance decreases the speed increases.

Accept 'there is a negative correlation (between them)' do not accept 'they are inversely proportional'

(iii) What conclusion on the relationship between the speed and the time taken to orbit the Earth can the student come to on the basis of this data? (1 mark)

As the speed increases the time (taken) decreases.

Accept 'there is a negative correlation (between them)' do not accept 'they are inversely proportional'

(Total 6 marks)