Photo: Yuri Levchenko (Flickr)
Today’s Moment of Science is about the ollie, the jump skateboarders use to jump over curbs, onto benches, or across chasms. The board seems to stick to the skater’s feet as he leaps. The jump is named after its inventor, Ollie Gelfand and here’s how it’s done.
As the skateboarder prepares to do an ollie he puts one foot in the center of the board, and the other foot on the tail. Then he drops into a low crouch. When he’s ready to jump he throws up his arms and jumps upward.
Being in the low crouch gives his body more distance to accelerate upward before his feet leave the ground. The height of the jump is determined by this upward acceleration: the faster the acceleration, the higher the jump.
As his body moves upward he stomps down hard on the tail of the board which causes the nose to rear up. A fraction of a second after he stomps on the tail it hits the ground hard, and bounces off the ground, pivoting the board in the opposite direction. Now the whole board is off the ground, and the skater and the board are rising together.
He slides his front foot forward to adjust the board’s position, and at the same time lifts his rear foot to allow the tail of the board to continue to rise. At the top of the jump the skater levels out the board with his feet, and board and skater descend together. As long as all this is timed just right the board and the skater’s feet seem to be attached to each other.
It has taken about a minute-and-a-half to describe this, but it all happens in less than a second.