Lisa Greathouse 
Bikes and Boards 

Readers will be amazed to discover that every time they climb onto bicycles and ride like the wind, they are defying gravity! This book explains the physics and history behind bicycles, skateboards, and surfboards. Readers learn what happens from the simplest movement of rolling forward to more complex tricks and stunts of jumping and spinning. Readers will never look at bikes, skateboards or surfboards the same way again.