What are some things to consider when deciding to use free weights or machine weiGhts

Well, Free weights are able to be used for anything and they don't cost much. Machine weights have to be adjusted to you body dimensions and they allow your joints to move in their natural paths. Most of all you should choose the best weight type that you are comfortable using and it can be worked in during your daily routine. 

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the plates spread at mid-ocean ridges (they are divergent plate boundaries) which allows magma to rise through the weakness between the plates. the magma then emerges as lava from the boundary and cools, creating a new crust.