A car is driving directly south down a road. It slows down to stops at a few stop signs, and then, accelerates up to 30 miles
per hour.
Is the car's velocity changing? Why or why not?

Yes, the car's velocity is changing because its speed is changing while driving.

hope this helps :)

The independent variable is the type of music.the dependent variable is the pulse rate.the intervening variable is the age of the subject.if the mother does not like rock, her pulse is likely to not increase.the same might be true for the sister.the friend may like rap and gets excited.to establish cause/effect relationship, all of the subjects must be consistent.hope i .