Unit 8 · The Physics of the Ollie

A playground seesaw is the easiest lever to picture. It is a long, stiff board resting on a bar in the middle. When one rider pushes down, the board turns around the bar, and the other rider goes up. A lever is any stiff bar that turns around one fixed point. Crowbars, scissors and bottle openers are levers too.

The fixed point a lever turns around is the fulcrum. On a seesaw the fulcrum is the bar in the middle. On Mr. Okafor’s ruler it was the edge of the desk. Every part of the lever swings around the fulcrum at the same time. When one end goes down, the other end must go up.

A lever has two other parts worth naming. The effort is the push you put in. The load is the thing being moved, such as the eraser or the other rider. Scientists study levers because they change how a push works. A small push in the right spot can move a heavy load, or a short motion can become a long one.

Set a skateboard on a carpet or on grass, where it cannot roll away. Put your hand on the tail, the short end that bends up behind the back wheels. Press down slowly. The tail sinks, the back wheels stay on the floor, and the nose at the front lifts into the air.

The board just acted like Mr. Okafor’s ruler. It turned around the place where the rear wheels touch the ground. That makes the rear wheels the fulcrum, or pivot, of the skateboard lever. The tail is on one side of the pivot. The rest of the board, with the front wheels and the nose, is on the other side.

This is the first thing that happens in an ollie, the jump where a skater and board rise together with no hands. The back foot presses the tail, the board turns around the rear wheels, and the nose comes up. Everything else in the ollie builds on this simple lever.

Watch two dots on a turning lever. One dot is near the fulcrum, and one is far away. Both dots turn through the same angle at the same time. But the far dot travels a much longer path. On a lever, the farther a point is from the pivot, the farther it moves.

A skateboard uses this. The tail is short, and the nose is far from the rear wheels. Here is a worked example with example lengths. Say the tail tip is 0.15 m behind the rear wheels and the nose tip is 0.53 m in front of them. The nose is 0.53 ÷ 0.15, or about 3.5 times, as far from the pivot.

For small turns, each point moves in proportion to its distance from the pivot. So if the tail tip drops 5 cm, the nose tip rises about 5 × 3.5 = 17.5 cm. A short stomp at the back becomes a big lift at the front. That lift is the ratio of the two distances at work, and it is why the ollie starts with the tail.

Try to open a heavy door by pushing right next to the hinges. It barely moves. Push the same door near the handle, far from the hinges, and it swings open easily. The push was the same size both times. What changed was the distance between your push and the turning point.

That turning effect has a name: torque. Torque tells how strongly a force makes something rotate around a pivot. It depends on two things: the size of the force and how far from the pivot the force acts. That distance is called the lever arm. A bigger force or a longer lever arm both give more torque.

Scientists write the rule as torque = force × lever arm. Force is measured in newtons (N), and the lever arm in meters (m). So torque is measured in newton-meters, written N·m. A push of 20 N on a door handle 0.8 m from the hinges gives a torque of 20 × 0.8 = 16 N·m. The same push 0.1 m from the hinges gives only 20 × 0.1 = 2 N·m.

A skater’s back foot can stand in different places. The bolts are the screw heads on top of the deck that hold each truck on. The rear bolts sit just a few centimeters from the rear wheels. The tail tip is much farther back. Where the back foot presses changes how much torque it makes around the rear wheels.

Here is a worked example with example numbers. Say the back foot stomps down with 400 N, about the weight of a 41 kg person, because 41 kg × 9.8 m/s² is about 400 N. Near the bolts, the lever arm might be 0.03 m. Torque = 400 N × 0.03 m = 12 N·m. On the tail tip, the lever arm might be 0.15 m. Torque = 400 N × 0.15 m = 60 N·m.

The same foot and the same stomp give five times the torque on the tail tip, because 60 ÷ 12 = 5. That is why skaters put the ball of the back foot on the end of the tail for an ollie. A skater who stands on the rear bolts and stomps will feel the board barely tip, just like the door pushed near its hinges.

A seesaw balances when the torques on its two sides are equal. A 300 N child sitting 2 m from the middle makes 300 × 2 = 600 N·m. A 400 N child sitting 1.5 m from the middle makes 400 × 1.5 = 600 N·m. The torques are equal and opposite, so the seesaw stays level. If one side’s torque gets bigger, that side goes down.

A skateboard works the same way, with the rear wheels as the middle. The back foot on the tail turns the board one way. The front foot, standing ahead of the rear wheels, turns it the other way. Say the front foot presses 200 N at a spot 0.30 m from the rear wheels, just behind the front bolts. That is 200 × 0.30 = 60 N·m against the tail.

That 60 N·m exactly cancels the 60 N·m stomp from the last lesson, and the nose would not rise at all. So in an ollie the front foot must go light at the moment the back foot snaps. The skater does this by starting to jump and lifting the front knee. The tail’s torque then wins, and the nose swings up.

The first skateboards of the late 1950s were often homemade: a plank with roller-skate wheels nailed or bolted underneath. Store-made boards appeared around 1959. Companies such as Makaha, started by Larry Stevenson in 1963, and Hobie sold boards in the 1960s. Most of these early decks were flat from end to end.

On a flat board, the back end is still a lever, but it is hard to use. The tail sits low and flat, so it has little room to swing down before it touches the ground. Skaters of the 1960s did tricks such as handstands, walking the board and spinning on the back wheels. They did not do ollies.

Larry Stevenson was granted a U.S. patent for a kicktail in 1971. A kicktail is a tail that bends upward at the back of the deck. It gave the back foot a clear place to press and turned the end of the board into a handy lever. Today most decks turn up at both ends, with a kicked nose as well as a kicked tail.

Look at a board from the side. The deck rides a few centimeters above the ground on its trucks and wheels. On a flat board, the tail tip starts at that same low height. When the tail is pressed, the tip touches the ground after only a small turn. The nose cannot rise very high before the turning stops.

A kicktail bends upward, so its tip starts several centimeters higher. Pressed down, it has farther to travel before it meets the ground. That means the board turns through a bigger angle, and the nose climbs higher. The upturned shape also lets the tip strike the ground hard and fast, which makes the pop, the sharp crack that starts an ollie.

The angle helps the foot too. A skater can feel the bend under the shoe without looking down. That makes it easy to put the ball of the back foot in the same spot every time. Doing a move the same way again and again is how a skater builds muscle memory, the feel for a motion that comes from practice.

Before practicing, buckle a helmet that fits snugly, wear flat shoes, and use wrist guards. Set the board on grass or a carpet so it cannot roll. Stand with the back foot’s ball on the tail and the front foot just behind the front bolts. Both feet point across the board. Regular skaters have the left foot in front, and goofy skaters have the right foot in front. Both are normal.

First, bend your knees into a low crouch. Next, snap the back foot down hard on the tail, as if stomping a bug. At the same moment, start a small jump and let the front foot go light. The tail should tap the ground with a crack, and the nose should flick up. Then let the board settle and step back onto it over the bolts.

Two problems are common. If the nose barely lifts, your back foot is probably too close to the bolts, so slide it back toward the end of the tail. If the board shoots out in front of you, you are pushing the tail forward instead of straight down, so aim the stomp at the ground. Practice ten pops at a time, and rest when your legs feel tired.

Push your palm against a wall. You can feel the wall pressing back on your hand. Isaac Newton described this in his book Principia, published in 1687. His third law of motion says that forces come in pairs. When one object pushes on a second object, the second pushes back on the first with an equal force in the opposite direction.

In an ollie, the tail tip slams down onto the ground. The tail pushes down on the ground. At that same instant, the ground pushes up on the tail with a force just as big. This upward push is called a reaction force. It lasts only a tiny moment, but it is large, because the tail hits fast and the hard ground does not give.

That quick upward shove at the very back of the board is the pop. It bounces the tail up off the ground and helps send the whole board upward. A soft surface, like thick grass, pushes back weakly because it squishes. That is why the pop sounds dull and feels weak on grass, and sharp on smooth concrete.

A skateboard has no glue on its top. If a rider stays heavy and stiff on the deck, the board cannot rise, because the rider’s weight pins it to the ground. So in an ollie the skater jumps. The jump starts almost at the same moment as the pop. The legs push the body up, then pull the knees toward the chest.

Pulling the knees up clears a space under the feet. The popped board rises into that space. Watched from the side, it looks as if the board is stuck to the shoes. Really, the board is flying up on its own, and the feet are staying just above it and guiding it.

This also explains a common problem. Some beginners pop the tail well but keep their legs straight. The nose comes up, then slams back down under their weight. The fix is to practice the jump on its own: crouch, spring up and tuck the knees high. Then add the pop. Falling is part of learning; if you lose the board, crouch low and roll instead of catching yourself with stiff, straight arms.

Rub your fingertip across the top of a skateboard. It feels like coarse sandpaper. That rough layer is grip tape: a sheet covered in tiny, hard grains, with a sticky back that glues it to the deck. Most grip tape is black, and skaters often cut and file its edges to match the board’s shape.

Grip tape is there for friction. Friction is a force that acts where two surfaces touch and resists them sliding past each other. The hard grains dig into the rubber sole of a shoe. That makes the shoe much harder to slide than it would be on smooth, painted wood.

There are two kinds of friction to know. The first, static friction, holds two surfaces still against each other, like a shoe planted while the skater rolls. Kinetic friction acts while surfaces are already sliding, like a shoe dragging along the board. Grip tape makes both kinds strong, so a foot can stay put, or it can pull the board along while it slides.

After the pop, the nose is pointing up and the back of the board is low. Now the front foot goes to work. The skater slides the outside edge of the front shoe, the little-toe side, forward along the grip tape toward the nose. This motion is called the slide, and it is what Maya’s slow-motion video showed.

Friction always acts against the sliding between two surfaces. The shoe moves forward and up along the board, so friction on the board points forward and up too. The rough grip tape lets the shoe drag the board along with it. The board rises with the foot, and its back end lifts off the ground to follow.

Kinetic friction can be estimated with f = μN. Here f is the friction force, N is how hard the surfaces press together, and μ (the Greek letter mu) is the coefficient of friction, a number for how grippy the pair of surfaces is. As a worked example, say a rubber sole on grip tape has μ = 0.9, an example value, and the shoe presses in with 150 N. Then f = 0.9 × 150 N = 135 N of drag on the board.

If the board only tipped nose-up, it would fall back down tail-first. The slide fixes this. As the front shoe reaches the bend of the nose, the skater pushes it forward and slightly down. That push makes a torque that turns the nose down and lifts the tail. The board swings level, which skaters call leveling out.

Meanwhile, the back foot rises with the tucked knee. It stays lightly over the tail as the tail climbs. Now the board is flat in the air, with both feet just above it. This is the top of the ollie, the moment that looks like magic in photos.

Two problems show up here. If the board stays nose-up and lands on its tail, the front foot did not slide far enough, so drag it all the way to the bend of the nose. If the nose dips first and the board lands front wheels first, the front foot pushed down too early or too hard. Grip tape also matters: worn-smooth or wet grip loses its friction, so the slide cannot pull the board. Replace worn grip, and skate only when the ground is dry.

An ollie has six parts in order: crouch, pop, slide, jump, level, land. Some of them overlap, but learning them in order helps. Before trying a rolling ollie, practice the whole motion standing still on grass or carpet. Wear a buckled helmet, flat shoes and wrist guards, and then move to smooth, dry, flat ground away from cars, rolling at a slow walking speed.

Step 1 is the crouch. With the ball of the back foot on the tail and the front foot just behind the front bolts, bend both knees deeply. Keep your shoulders over the board and in line with it, and look ahead. A deeper crouch lets the legs push for longer on the way up, so the jump has more power.

Step 2 is the pop. Snap the back foot straight down on the tail so the tip cracks against the ground. Think about a quick, hard snap, not a slow press. A fast strike makes a big, short reaction force from the ground. That is what bounces the tail up and starts the board rising.

Step 3 is the slide. As soon as the tail cracks, the front shoe starts dragging forward along the grip tape. The outside edge of the shoe leads the way toward the nose. Your slow-motion video, if you film one, will show the slide starting just a few frames after the pop.

Step 4 is the jump. In real time it happens almost together with the pop and slide. Spring up out of the crouch and pull both knees toward your chest. The back foot rises with the climbing tail. The front foot keeps sliding as the knees come up. The pop, the slide and the jump overlap, and that is why they feel like one move once you know them.

A useful drill is to practice these steps with the board still on carpet or grass. Say each word aloud as you do it: pop, slide, jump. Start slow and small. When the order feels natural, try it rolling slowly. Feeling nervous before your first rolling ollie is normal. It is your body asking you to take smaller steps, so go back to standing still whenever you need to.

Step 5 is the level. At the top of the jump the front foot pushes forward at the nose, and the board flattens under both feet. The skater keeps the knees tucked and the eyes on the board’s bolts. This is the highest point of the ollie.

Step 6 is the land. Gravity brings the skater and board back down together. Set both feet down over the bolts, not on the tail or the nose. Feet over the bolts press straight down on the trucks, so the board stays level and rolls away smoothly. Bend your knees deeply as the wheels touch, and keep your shoulders over the board.

Many first landings end with a foot off the board. That is normal. If you are falling, step off, crouch low and let your knee pads take the slide, or roll onto your side. Do not reach out with straight arms. Each try teaches the feet a bit more about where the board will be, so the landings get steadier with practice.

Balance a ruler on one finger. There is one spot where it stays level. That spot is the ruler’s center of mass, the point where its mass acts as if it were all gathered together. A standing person’s center of mass is usually inside the body, a little below the belly button.

When a skater crouches, the center of mass drops lower. When the skater springs up, it rises. Once the skater and board leave the ground, gravity is the main force acting on them. From that moment, the path of the center of mass is set. Waving the arms or tucking the knees cannot make it go higher or come down later.

Tucking still matters, though. Pulling the knees up raises the feet closer to the center of mass. So the feet and board rise more than the center of mass does. A skater whose center of mass rises 30 cm can lift the board even higher by tucking well. That is why good ollies look so tall.

Toss a ball gently forward and watch its path. It climbs, curves over the top and comes back down in a smooth arch. That shape is a parabola. Any object moving freely through the air, with gravity as the only big force, follows a parabola. A skater’s center of mass does too during an ollie.

Gravity changes the up-and-down speed by 9.8 m/s every second. On the way up, the skater slows down until, at the top, the up-and-down speed is zero for an instant. That top point is the peak. On the way down, the skater speeds up again. The trip down mirrors the trip up, so the rise and the fall take the same time.

Here is a worked example. A skater leaves the ground moving upward at about 2.4 m/s. Height after time t is 2.4t − 4.9t², in meters. After 0.10 s: 2.4 × 0.10 − 4.9 × 0.01 = 0.24 − 0.049 ≈ 0.19 m. After 0.25 s: 0.60 − 0.306 ≈ 0.29 m, which is the peak. With the speed rounded to 2.4 m/s, the peak lands just under 0.30 m. The table shows the full curve.

In a rolling ollie the board and skater are moving forward before the pop. Newton’s first law says an object keeps moving at the same speed in the same direction unless a force changes it. That tendency to keep moving is called inertia. In the air, nothing pushes the skater or board forward or backward much, so both keep their forward speed.

That is why the board stays under the feet. The skater and board started with the same forward speed, and they keep it together. Here is a worked example. If they roll at 3 m/s, an example speed, and stay in the air 0.49 s, they both travel 3 × 0.49 ≈ 1.5 m forward. They land together, about 1.5 m down the court.

Put the up-and-down motion together with the steady forward motion, and you get the parabola. The forward part stays the same, and the up-and-down part rises and falls. Air pushes back a little on both, but at slow skating speeds that push is small. A skater who leans back or pushes the tail forward during the pop changes the board’s speed, and the board rolls away ahead.

A skater’s hang time is how long a skater stays in the air during a jump. It depends only on how high the center of mass rises. For a jump that rises a height h and lands at the same level, hang time = 2√(2h ÷ g), where g = 9.8 m/s². The 2 out front is there because the trip down takes as long as the trip up.

The table shows worked results for five heights. Notice how hang time grows. Going from 0.10 m to 0.40 m is four times as high, but the time only goes from 0.29 s to 0.57 s, about twice as long. That happens because of the square root. Gravity speeds up a falling object every moment, so each extra centimeter of height adds less extra time.

This is why even big ollies are short. A very high ollie of 0.50 m gives about 0.64 s in the air. Pros look as if they float, partly because tucking lifts the board higher than the center of mass. But physics keeps every flat-ground ollie well under one second.

Let’s work out the hang time of a 30 cm ollie step by step. First change centimeters to meters: 30 cm = 0.30 m. Next find 2h: 2 × 0.30 = 0.60. Then divide by g: 0.60 ÷ 9.8 ≈ 0.0612. The square root of 0.0612 is about 0.247. That is the time to rise, in seconds.

Finally, double it for the trip down: 2 × 0.247 ≈ 0.49 s. So a rider whose center of mass rises 30 cm stays in the air about half a second. About 0.25 s goes to rising and about 0.25 s goes to falling.

This matches the story’s video. At 240 frames per second, 0.49 s fills 0.49 × 240 ≈ 118 frames. The frame count, 118 ÷ 240 ≈ 0.49 s, and the hang time rule give the same answer. Checking a calculation against a real measurement like this is how scientists test whether a rule works.

Jump off a low step and land with stiff legs, and you feel a jolt. Land with bent knees, and it feels soft. The difference is time. To stop a falling body, a force has to take away its downward speed. If the stopping happens quickly, the force must be large. If it takes longer, the force can be small.

From a 0.30 m rise, a skater comes down at about √(2 × 9.8 × 0.30) = √5.88 ≈ 2.4 m/s. Take a 50 kg skater as a worked example. Stiff legs might stop the fall in 0.05 s. The slowing is 2.4 ÷ 0.05 = 48 m/s², so by F = ma the force is 50 × 48 = 2,400 N. Bent knees might stretch the stop to 0.25 s: 2.4 ÷ 0.25 = 9.6 m/s², and 50 × 9.6 = 480 N.

These are the extra forces needed to stop the fall, on top of the skater’s own weight. Bending the knees cut the force to one fifth, because the stop took five times as long. This is the same idea behind knee pads, helmets and the soft foam inside them: each one makes a hit last longer, so the force is smaller. To absorb a landing means to spread it out over time.