Newton’s first law states that bodies have a property called inertia, which means that once given a velocity, they will travel at that same velocity forever, unless acted upon by some outside force. T...Newton’s first law states that bodies have a property called inertia, which means that once given a velocity, they will travel at that same velocity forever, unless acted upon by some outside force. This behavior caused Aristotle to believe a moving body was filled with some sort of substance that was “used up” as the body moved. But in spite of observations like this, Newton was able to deduce that this slowing of an object is due to an external force (friction), and that
