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Homework Statement ""If the coefficient of thermal expansion of steel is 1.1 x 10^ -5 ℃^ -1 and a railway rail is 4. 5 m long, how much would the length Δ L of the rail increase by if the temperature changes from -10 ℃ to 30 ℃? "" Could anyone direct me to a youtube video, or something...

Homework Statement """" a) The price of gold, according to << Link removed by Moderator >>is currently $27 per gram. It is estimated that over the course of history about 170,000 tonnes of gold has been mined, what would the current price of all this gold be? b) The density of gold...

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Homework Statement I'm having trouble with this. I need to calculate the number of atoms in iron. How do I do this? For example if I had 1 KG of iron, how many atoms are in it? Homework Equations I need to give an answer in scientific notation A x 10^B A being 1 significant...