# miss

## miss

• Submitted By: oliviiaaa
• Date Submitted: 10/06/2015 2:09 PM
• Category: Science
• Words: 640
• Page: 3

Missing figures

Brief History of Skateboarding.

In the beginning, skateboarding consisted of a 2x4 and some old roller-skate wheels. Around the 1950's with the boom in the surfing popularity, skateboarding became more popular. During this time it was known as sidewalk surfing. In the 1960's is when skateboarding really took off. This is when the first skateboards were produced and sold. During this time period skateboarding consisted of cruising around the streets on your board. In 1978 a 15 year old boy by the name of Alan "Ollie" Gelfand invented a trick he called the no-hands air. His friends named after him the ollie. This was a ramp based trick. In the coming years a rider by the name of Rodney Mullen took the trick and applied it to flatland skateboarding. After this point skateboarding began to evolve in to the sport it is today. Virtually every trick in the modern day skateboarding involves the ollie.

When a skateboarder rolls down the street they have forces acting in the X and Y direction. The forces that I will focus on are only in the Y direction. As a skater rides down the street there are three forces acting on the skateboard. The red arrows in the image indicate the force of gravity on the mass of the skater(Mg). The black arrow represents the force of gravity on the skateboard(mg). The blue arrows are the FN or natural force of the ground pushing up on the wheels of the board. These forces have a net force of zero.
Sum of forces in Y: Mg + mg - FN = 0

As the skater prepares to ollie they lower the center of gravity by bending at the knees and waist. Next the skater will begin to explode in the positive Y direction by pressing down on the tail of the board. The red arrows now have an uneven distribution to the tail of the board causing lift on the nose. All of the FN is now pushing up on the rear wheels.

At this point the skater is has applied a large downward force on the tail causing the board to pop or bounce off of the...