a system of measurement based on units of ten; used in most countries and in all scientic work
the number of units that fit along one edge of an object
the number of unit squares that fit inside a surface
the amount of matter in a given space; in the scientific terms, density is the amount of mass in a unit of volume.
the measure of the pull of gravity between an object and earth.
a force of attraction, or pull, between all objects.
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