[sergiosgc]

When speed is zero, distance is zero and energy/distance is infinite. Hence the OP questioning how could the graph present a finite value at that point.

Personally, I'd wager they followed the old scientific adage: "If you wish your function to be linear, sample two and only two points".

[lutusp]

> When speed is zero, distance is zero and energy/distance is infinite.

1. Not energy/distance, but energy/speed.

2. Notwithstanding the cart's labeling ("Wh/mi"), its values aren't predicated on a division of energy by speed. "Wh/mi" doesn't literally mean mean "watt-hours divided by miles per hour", it means "the relationship between watt-hours and vehicle miles per hour".

> Personally, I'd wager they followed the old scientific adage: "If you wish your function to be linear, sample two and only two points".

Yes, except the chart isn't linear. Just for fun, here's a polynomial function that matches the chart's results reasonably well:

    f(x) = 0.03165008148658699 * x^2
         + 0.2559872636164877 * x
         + 106.19966024840329

Here's the resulting chart:

http://i.imgur.com/rLmaN90.png

So ... no division by zero. BTW I worked this up with the help of Sage, my current favorite, free math tool:

http://www.sagemath.org/