How does an ollie work physics

It's lumpy and weird. This means that gravity isn't the only force affecting the skateboard. Unlike a soccer ball in mid-flight, a skateboard mid-ollie is being actively steered. This is exactly what makes doing an ollie so hard. It's not enough to get the skateboard up into the air - you also have to steer it while it's in the air.

In fact, we can work out how you need to steer the skateboard. Tracker has a nice feature that we'll call 'force arrows'. These arrows show you how much force acts on an object at every instant, and in which direction the force acts. So for example, if you were to kick a ball into the air, while the ball was mid-flight, this arrow would always point down and be the same length, even though the ball is moving forward.

That's because the only force acting on the ball is gravity, which pulls it straight down, and acts with a constant strength. For those of you who've studied physics, these arrows denote the acceleration of the center of mass, which by Newton's second law is proportional to the net force acting on the skateboard.

It's a neat piece of science art, and it also tells us something interesting. Free-body problem: how do skateboarders do an "ollie"? Want to read more? Register to unlock all the content on the site. E-mail Address. Hamish Johnston is an online editor of Physics World. Physics World Careers Providing valuable careers advice and a comprehensive employer directory. No matter how hard you push down, the launch engine shuts off the instant the tail pops.

This means to get the highest Ollie you should use a board that allows the nose to rise considerably before the tail strikes the surface. This favors boards with inclined tails and shorter tails. On the other hand, if the tail is too short or too steep this will give you less leverage and impair your ability to perform a rapid down kick.

When I first learned the move, I was using a lighter board with a moderate kicktail. When Alan Gelfand worked out the move, he found a wider, heavier board with longer tail is what worked for him. His signature board even had the front truck and wheels mounted very close to the nose.

The reason for these differences was I learned the move on steep banks and flat ground while he learned it on vert. If you do a hard dynamic hop near the lip of a pool or half pipe—by kicking down the tail aggressively to get the board to move away from the surface as fast as possible—you risk floating too far out and landing down on the transition. This allowed him to become the first person to consistently pull off big Ollies on vert.

In contrast, I could do them well in those terrains, but early on I tended to hop too far off from the wall when I did them on vertical, which made for some interesting landings. The takeaway is board design influences how well you can ollie because it governs how fast and how far you can make the board move away from the surface. Depending on your style and the kind of terrain you will be skating, faster is not necessarily better.

The other primary factor limiting your maximum attainable height on flat ground is how high you can jump. If you kick down on your tail forcefully and step out of the way, the board will rise higher than you can leap straight up. This means your Ollie height is not only limited by how high you can make the board rise, but also by how high you can jump up with your board as you launch it. You can leap higher if you squat first, but this makes it more difficult to get the foot movements right.

Rodney Mullen was apparently the first person to figure out those movements and consistently do high Ollies from flat ground. Rodney was a freestyle skater who saw opportunities to do new tricks by doing higher Ollies on flat ground. His technique expanded the envelope on what was possible and helped street skating flourish after the parks were demolished.

He does this by rotating his upper body and lower body in opposite directions. This way he can land with the board facing the other way, while still adhering to the physical requirement that the angular momentum of the system remains zero. As shown in the figure above, he gives his upper body a clockwise rotation, resulting in an angular momentum for his upper body equal to H 1.

At the same time he gives his lower body including the skateboard a counterclockwise rotation, resulting in an angular momentum for his lower body plus skateboard equal to H 2.

The key is for him to generate a high enough H 1 so that his lower body including the skateboard must match this value with H 2 by rotating degrees in the other direction. He does this by extending out his arms as he is airborne. Once the skateboarder lands on the ground he simply rotates his upper body back around so that he now faces the wall. He is able to do this because after landing he is able to exert a torque against the ground, allowing him to rotate his body back around so that he is now facing entirely in the opposite direction to before.

Physics Of Skateboarding — Pumping On A Half-Pipe Pumping on a half-pipe is used by skateboarders to increase their vertical take-off speed when they exit the pipe. This enables them to reach greater height and perform more tricks, while airborne.

The figure below shows a skateboarder approaching the curved portion of the half-pipe. In other words, his feet never have to leave the board. This begs the questions; what is the physics taking place, and how does the skater increase his speed without pushing off the ground? To increase his speed, the skateboarder crouches down in the straight part of the half-pipe as shown in the figure above. Then when he enters the curved portion of the half-pipe he lifts his body and arms up, which results in him exiting the pipe at greater speed than he would otherwise.

The basic skateboarding physics behind this phenomenon can be understood by applying the principle of angular impulse and momentum. The schematic in this analysis is given below. Where: w i is the initial angular velocity of the body consisting of skateboarder plus board , at position 1 w f is the final angular velocity of the body, at position 2 , which is the point at which the skater exits the half-pipe V i is the initial velocity of the center of mass G of the body, at position 1 V f is the final velocity of the center of mass G of the body, at position 2 r i is the initial distance from the center of rotation o to the body's center of mass G , at position 1 r f is the final distance from the center of rotation o to the body's center of mass G , at position 2 g is the acceleration due to gravity N 1 and N 2 are the normal forces acting on the wheels, as shown F 1 and F 2 are the friction forces acting on the wheels, as shown It is assumed that the half-pipe is a perfect circle with center at o.

The physics can be analyzed as a two-dimensional problem. These moments are integrated between an initial time t i at position 1 and a final time t f at position 2 Here we are assuming that the body can be treated as rigid at positions 1 and 2 , even though the skater does in fact change his moment of inertia between these two positions. But as it turns out, when using this equation we only need to know the initial and final values of the moment of inertia of the body.

The line of action of the normal forces N 1 and N 2 pass through point o , so they do not exert a moment on the body about point o. The friction forces F 1 and F 2 are small so they can be neglected in terms of their moment contribution.