Light travels in a straight line because it doesn't usually interact with its medium. When it does it is called refraction.
Inertia- a property of matter by which it continues in its existing state of rest or uniform motion in a straight line, unless that state is changed by an external force.
<span>graphite (2.16 g/cm3)
glycerin (1.26 g/cm3)
copper (8.9 g/cm3)
silver (10.5 g/cm3
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