T. H. Baer 
Medir la velocidad (Measuring Speed) [PDF ebook] 

When a bird flies by a window or a car zooms by on the highway, we often wonder how fast the two objects traveled. This book explains the concept of speed to readers while showing them accessible ways to measure it for themselves. Learning the amount of distance traveled, and how quickly that distance was covered, is a great way to implement a variety of STEM topics while practicing this essential mathematical skill.