Young skate boarder David spends a day at the skate park with host Nykeem and guest pro Erik learning about thrust and drag. Dr. Heather explains that thrust is created when an upward force on an object is powerful enough to counteract gravity. Skaters get thrust when they do an 'ollie', slamming the curved tip of the board downwards with their foot, creating thrust. A skate board is a compound machine (2 or more simple machines working together) with a system combining polyurethane wheels and curved tips on the board which act like levers. The sport began in the 1950's when surfers in California adapted their ocean sport for the streets.