# Physics of Skateboarding

The reason I chose this topic was because I always wanted to know what makes a skateboard go down and move the way it does.  I also used to skateboard as a child and so the interest has stuck with me for the last 4 or 5 years.  I always wondered how fast I could go if I were to try to roll in from a higher drop.

Skateboarding is an action sport that involves riding and performing tricks on a skateboard.  A skateboard is made of a wooden deck, grip tape, trucks that connect the board and wheels, and the wheels allow you to roll.  Skateboarding involves rolling down a hill and that is what allows you to gain momentum and speed and allows you to do tricks like kickflips, heel flips, ollies, grinding, etc.

The Hippie Jump

One trick you can do on a skate board is a hippie Jump. "In this trick the skater must propel himself up by pushing vertically down with his legs. If he pushes on the board with even the slightest horizontal force the board will shoot out either in front of him or behind him." ("The Physics Of Skateboarding")  With this trick you can use the projectile motion equations where the vertical component of velocity changes and because gravity is only horizontal.  You can use an equation like h=1/2at^2+v0+h0.  You also can find the friction to see how the board stays down on the ground.

Example: If you are rolling with an initial velocity of 7cm/s and an acceleration of 4cm/s with no initial height and it takes 3 seconds to jump, how high can you get?

The equation would be .5(4)(3)^2+7+0 which would equal 25 cm in the air.

# The Ollie

The ollie is a trick on the skateboard where the rider jumps with the board in the air while riding or standing still and allows the rider to jump on to ledges.  During the ollie the forces change during the trick.  During this trick the skater pushes down on the back end of the board while sliding the foot upward with friction so the rest of the board comes up.  The upward force of the pavement also brings the board up.  As you come to a stop in midair, gravity begins to work and brings you back to the ground.  "Also, gravity pulls down the center of the mass." (Physics of the Ollie; Doherty, Paul).  You can use kinematics equations to see how far you can get after you take off.  Use the equation h=1/2gt^2+v0t+h0 to determine the height you will achieve when you have a forward acceleration and then ollie.

Example:  If you are standing still on a skateboard with no initial velocity or height and it take you 3 seconds to do an ollie trick, how high will you get when you land the trick?

The equation would be h=.5(9.8)(3)^2+0+0 which would equal 42.75 cm in the air.

# Mid-Air Maneuvers/Frontside 180

"A skateboarder launches straight into the air from the top of a ramp. Seeming to hang in place for just a moment, he turns in mid-air and directs himself back down the ramp. Skaters call this maneuver a frontside 180. Physicists call it impossible. Well, they don't really call it impossible. Just very, very sneaky." (Skateboard Science, Exploratorium).  When you turn your body in mid-air you are proving the law of conservation of angular momentum.  The only thing that can stop you is torque which you use in this.  So you use momentum to turn and torque to stop while all in midair.  In the air you need your upper body and lower body's torque to all equal zero so the equation T1 (upper body) + T2 (lower body)=0.

# Works Cited

"Ollie_physics." Ollie_physics. N.p., n.d. Web. 05 June 2014.

"Physics Of Skateboarding." Real World Physics Problems. N.p., n.d. Web. 05 June 2014.

"Skateboarding - Extreme Skaters." Extreme Avenue. N.p., n.d. Web. 05 June 2014.

"Skateboarding Tricks: The Ollie | Exploratorium." Exploratorium: The Museum of Science, Art and Human Perception. N.p., n.d. Web. 05 June 2014.