 # GCSE level questions on the Earth in Space Q9. A satellite is in a circular orbit around the Earth. The diagram below shows the velocity of the satellite at two different positions in the orbit. (a) Explain why the velocity of the satellite changes as it orbits the Earth.

[3 marks]

(b) The graph shows how the length of a satellite orbit depends on the height of the satellite above the Earth's surface. A satellite orbits 300 km above the Earth's surface at a speed of 7.73 km/s.

Calculate how many complete orbits of the Earth the satellite will make in 24 hours.

[5 marks]

(c) In 1772, an astronomer called J Bode developed an equation to predict the orbital radii of the planets around the Sun.

The table shows Bode's predicted orbital radii and the actual orbital radii for the planets that were known in 1772.

 Planet Predicted orbital radius in millions of kilometres Actual orbital radius in millions of kilometres Mercury 60 58 Venus 105 108 Earth 150 150 Mars 240 228 Jupiter 780 778 Saturn 1500 1430

(i) The predicted data can be considered to be accurate. Give the reason why.

[1 mark]

(ii) Bode used his equation to predict the existence of a planet with an orbital radius of 2940 million kilometres. The planet Uranus was discovered in 1781. Uranus has an orbital radius of 2875 million kilometres. Explain why the discovery of Uranus was important.

[2 marks]

(Total 11 marks)