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Duration:03:11
Uploaded:2016-08-29
Last sync:2018-04-23 14:50
If most people got on a skateboard, they would roll forward slowly for a few feet, then fall down and break their wrists. But there are a proud few who can do some pretty amazing tricks on a board, and they use physics to pull them off. Today we're going to learn about the most humble of tricks, the ollie.

Hosted by: Michael Aranda
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Sources:
References
http://www.real-world-physics-problems.com/physics-of-skateboarding.html
http://www.exo.net/~pauld/Skateboard/ollie_physics.html
http://www.exploratorium.edu/skateboarding/trick02.html
http://www.wired.com/2014/10/skateboard-physics-empzeal/
http://wonderopolis.org/wonder/how-do-you-ollie
http://www.olliebook.com/appendix/ollie-physics-and-science/
Images
https://en.wikipedia.org/wiki/File:Ollie_skateboarding_trick.jpg
[SciShow intro plays Intro]

Michael: Skateboarding can be tricky. There's more to riding than just rolling along. things like jumping, kicking and popping. Those are actual skateboarding terms and you do all of them in one of the most fundamental skateboarding tricks out there: the Ollie.

To do an ollie, you try to jump in the air, while also keeping your skateboard attached to your feet. But there's no glue and no straps, and you don't physically grab the board, so it's not quite as simple as jumping. In fact, if you tried to jump straight up the would keep rolling along the ground, which is a totally different trick called the Hippie Jump.

So when you do an Ollie, how do you get the board to actually leave the ground without picking it up? It all comes down to a few principals physics: force, torque, Newton's third law, and friction. When you're skateboarding, you mainly want to control two factors, the net force and the net torque on the board.

Forces push and pull objects in a certain direction, like how the force of gravity pulls the board down. Torques rotate objects in a certain direction, normally around what's known as a pivot point. And you use both force and torque to do an Ollie.

The first step of an Ollie is jumping, but it's a special kind of jumping. You bend your knees and then quickly straighten them out, essentially pushing down on the ground. But Newton's third law says that for every force you apply, there will be an equal and opposite force applied back onto you. That means the ground will push back with an equal and opposite force, which accelerates you into the air. But you want the skateboard to leave the ground too, so the skateboard also has to push down on the ground, so that the ground can push the board back.

That's where the jump gets a little more complex. After you bend your knees, you purposely straighten out your back leg so that you push down on the very back of the board, what's known as kicking. The board pushes against the ground and again, thanks to Newton's third law, the ground pushes the board back sending it flying into the air. In skateboarding, that's called popping.

But while all of this is happening, you're also affecting the torque on the board. When you push down at the back of the board, the back wheels become a pivot point. The back of the skateboard rotates down, and the front of the board rotates up. That leaves the board at an angle with the front way higher than the back. Which is actually pretty handy because in the next step you use friction to move the board even higher.

If the board has good grip, there can be a lot of friction between your shoes and the board. Friction is a force that opposes motion between two surfaces. If you try to slide your front foot upward, the friction force keeps the board from slipping past your shoes. So as you move your foot upward, you also end up moving the board upward, it's like the board is stuck to your feet.

Now your Ollie has reached maximum height, but you still have to get your board straight again, so you push your front foot down, creating a torque on the board again. This time the center of the board acts as the pivot; the front of the board goes down, and the back of the board moves up. If you time all of this just right, you're level with the ground but hopefully high above it.

Now all you have to do is let the forces of gravity take you back down to the ground, making sure your knees are a little bent and ready for the impact. Once you're an expert at the Ollie you can try and spice it up. You could try and apply torque to the left, or to the right, so the whole board flips over while you're in the air; that's a kick-flip or a heel flip depending on the direction of the flip.

The only way you're truly going to master these tricks is by going out and practicing, so get out there and do some skateboarding science.

Thanks for watching this episode of SciShow which was brought to you by our patrons on Patreon. If you want to help support the show just go to Patreon.com/SciShow, and don't forget to go to YouTube.com/SciShow and subscribe.