On the Run

Tell me about skateboards... I invited a 6th grader to show me his Ripstick which is a two wheeled skateboard. He brought it to my PE class and we all tried it. I finally got the hang of it. The student navigated all the way up a nice long inclined sidewalk by wiggling on it back and forth. We gave him some applause. How does a "long board" with four wheels act differently than a two wheeled Ripstick?