Editor's Note: The Hyperloop is a totally imaginary transportation device that has captivated entrepreneur Elon Musk, who keeps talking about it. First imagined at least 100 years ago, it would ...

Velocity-time graphs show how the velocity (or speed) of a moving object changes with time. These graphs also show if the object is moving at a constant speed or accelerating, decelerating, or still.

At one point in the past, I was a teenager. Hard to believe, I know, but it's true. During that time, I thought about teenager things. In particular, I recall thinking about and wanting a super fast ...