1. The problem statement, all variables and given/known data A skateboarder on a horizontal surface can accelerate from rest just by moving the body, without touching external support. Investigate the parameters that affect the motion of a skateboard propelled by this method. 2. Relevant equations Don't know what variables I can test.... 3. The attempt at a solution I've looked at some experiments regarding rolling friction, motion and centre of mass. but can't draw any conclusions from them.