- Let’s adopt the “
**rightward is positive**” convention for the motions below

- Since the sheep is moving rightward and speeding up, its velocity is represented by more and more
**positive**numbers. - Since the velocity is becoming more positive, the acceleration is
**positive**.

–

- Since the sheep is moving leftward and speeding up, its velocity is represented by more and more
**negative**numbers. - Since the velocity is becoming more negative, the acceleration is
**negative**.

–

- Since the sheep is moving rightward but slowing down, its velocity is represented by less and less
**positive**numbers. - Since the velocity is becoming less positive, the acceleration is
**negative**.

–

- Since the sheep is moving leftward but slowing down, its velocity is represented by less and less
**negative**numbers. - Since the velocity is becoming less negative, the acceleration is
**positive**.

- In a nutshell, the speed increases if the velocity and acceleration have the same sign, and decreases if the velocity and acceleration have opposite signs.