A car starts 10 m north of a reference point. It moves at a constant velocity over the next 5 s, reaching a position of 10 m south of the reference point. What is the car's average velocity?

  v = -4 m / s

Explanation:

The average speed of a body is defined by the distance traveled in a given time interval

     v = (x₂ -x₁) / (t₂ -t₁)

in this case the end point is x₂ = -10 m and the start point is x₁ = 10 m, the negative sign is because the point is below the reference that can be considered as zero point

let's calculate

     v = (-10 - 10) / 5

     v = -20 / 5

      v = -4 m / s

if they have a finite resultant

energy can be converted from one form to another, but it cannot be created or destroyed in ordinary chemical or physical means. do not understand what you are asking but hope this