1. Estimate the volume of the rock, giving reasons for you answer.
2. Let's say that 1 cubic metre of rock has a mass of 2.5kg. Calculate the mass of rock in these spoil heaps in kg.
3. Suppose that the rock was dug up from 100 metres underground and hauled up. (Perhaps not unreasonable after consulting http://www.cumbria-industries.org.uk/a-z-of-industries/copper/) Calculate the gravitational energy gained by the rocks using a formula mass x g x height. g is called the gravitational field strength and is 10N/kg on Earth.
4. Suppose that the energy to lift the rocks (ie to give them the energy you just calculated) came from petrol generators. Generators are probably about 30% efficient, which means that only 30% of their energy woild go to lifting the rocks. The rest is wasted as heat and sound. So calculate the petrol energy needed to cover lifting the rocks and all the wasted energy.
5. Petrol has an energy density of 32.4 kg per litre. Calculate the number of litres of petrol needed.
6. Calculate the cost of all of that petrol.
7. Find out the price per kg of copper at the moment and calculate the mass of copper you'd need to dig up to make it worth shifting all of those rocks. Could this mine be economic?
