Changes

[[File:Centre_of_mass_train.png|right|300px|link=https://www.amazon.co.uk/gp/product/B001ELZ6F8/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=B001ELZ6F8&linkCode=as2&tag=nrjc-21&linkId=91947c71f7b82fcaf986f96327cd542d|thumb|This toy balances by having its It was essential to find the '''centre of mass''' directly of an old steam train to make sure it was low enough that it wouldn't tip over its beakon the tracks at a turn. There are two points where the '''centre of mass''' was found. One when the boiler was empty and one when it was full.]]