Why can friction make observing newtons first law of motion difficualt?

Answer 1

Newton's First Law states, more or less, that if an object is in motion, the "natural thing" for the object to do is to continue moving. Everyday observation, on the other hand, shows that objects that are moving tend to slow down. The discrepancy is simply due to the fact that Newton's First Law assumes that no forces (or no net force, in any case) act on the object. When there is friction, there is indeed a net force.