How A Pogo Stick Works

How a Pogo Stick Works The pogo stick is a mechanical device that utilizes the spring's ability to store energy. In this paper I will explain how the toy uses the laws of physics to provide hours of fun. There are a lot of forces acting on you and the pogo stick as you bounce along. We'll take an in depth look at all of these forces and what part they play in the overall functioning of pogo sticks. The physical aspects can be broken down into sections to get a better understanding of what is going on.

Pogo sticks have been around for a long time. They were very popular during the 60's and 70's. People would spend all day hopping around their driveway on the pogo stick. The pogo stick was like having a power wheels for the eighties generation. The fact that you can still see pogo sticks being used by kids around the world proves that it truly was a great idea.

How exactly does a pogo stick work? The person who is operating the pogo stick stands on the two pedals at the bottom of the stick. Once they are balanced and ready to start bouncing the person applies a downward force on the pedals. When they push down it causes the spring to become compressed. The stored energy in the coils of the spring is elastic potential energy. This extra energy provides the pogo stick with an extra amount of force on it's way back up. With the uncoiling of the spring it releases kinetic energy causing you to get a higher bounce while doing the same amount of work with your legs because of the spring.

First, I want to look at what a spring is and how exactly it works to create a mechanical advantage. Also, we need to be able to understand all of the forces involved in the operation of a pogo stick. There are a lot of different forces acting on you and the pogo stick that you may have not thought of. For instance there are gravitational, normal, and frictional forces that all help. The spring in the bottom of the pogo stick is a device that is capable of storing energy due to a restoring force. The energy that is stored in the spring is called elastic potential energy. Then released as kinetic energy when the spring goes back to its equilibrium.

The spring is a coil of metal that can provide a mechanical advantage. When a spring is at rest and has no other forces acting on it there is an equilibrium point. This is the point on a spring where it goes back to if you compact or stretch out the spring. You can use springs to store elastic potential energy for later. For instance if you take a spring and compress it then let it go it will restore itself to its equilibrium position. The equilibrium point also allows you to tell how big of vibrations the spring is making. Manufacturers make springs in various shapes and sizes. The most common type of spring as a toy is the slinky. Some have very tightly compressed coils and others are made with loose coils. For the pogo stick however, you need to have a very strong and rigid spring to make a big difference with the weight of a person. If you had a loose spring that was very easy to compress then you would not be able to store as much energy in it.

One type of a physical property is the friction force. Frictional forces are what keep you from sliding off the pedals of the pogo stick. If there was no friction and you came down at even the slightest angle you would slip right off. The pogo stick is designed with rubber pads on the pedals to create extra friction. Another import aspect when describing how a pogo stick works is the friction force between the tip at the bottom of the pogo stick and the ground. This part of the stick has a rubber pad attached to it as well. For example if you wanted to move forwards, you would tilt the pogo stick at a forward angle. When you angle it the bottom of the stick tries to go behind you, but because of strong frictional forces created by the rubber and the ground the friction then pushes you forwards. But what if there was no friction? If you had no friction the bottom of the stick would slide straight out from under you, which could result in a very nasty face plant.

Normal forces are forces that determine which way you go and at what velocity you travel. When you get on the pogo stick and get your balance you then jump up pulling on the handles to keep your feet in tact with the pedals. When you push down against the earth you a exerting a normal force equal to the weight of your body plus the pressure that you exert downward on the pedals. However, those are not the only forces that are acting on you. The earth is also exerting a force on you or else you would go into the ground. The earth exerts a force that is equal to the normal downward force that you are exerting on the earth. These normal forces are equal and therefore they make up an action-reaction pair. Action-reaction pairs come from Newton's third law of motion, "For every force that one object exerts on a second object, there is an equal but oppositely directed force that the second object exerts on the first object"(Bloomfield, p. 24). The stored energy in the spring also creates another normal force upward on you and the pogo stick. The spring makes it easier for you to jump off the ground by creating a small, but extra amount of upward force.

Gravitational forces are the forces that are naturally occurring whether you are doing any work or not. For instance, the force the earth exerts on your body is equal to your mass times 9.8m/s. This force is very noticeable on you because the earth is so large and your body is very small in proportion. You exert an equal force on the earth as well. When any to forces are equal to each other then they are classified as action-reaction pairs. So by Newton's laws you are exerting the same amount of force on the earth. Every body in the universe has an attraction to another object no matter how small or large that force may be. When you want to go somewhere on a pogo stick it is essential to get off the ground. To get off the ground you must overcome earth's gravity by creating a larger upward force than that of the downward force. The spring at the bottom of the pogo stick helps you do this easier. But what if you wanted to turn the pogo stick in a direction other than straight ahead? In order to turn you have to push off the ground at the angle at which you wish to travel. This may be hard for beginners because it becomes tricky trying to keep your balance while turning.

Balance is another important aspect to riding a pogo stick successfully. It is very important to keep your center of gravity over the point on the bottom of the stick. If you lose your balance it is very hard to regain because you have such a small point-of-contact with the ground.

When you want to move on a pogo stick it requires that you do work. But, how much of that work are you doing and how much does the spring do? If you get on the pogo stick and balance yourself against a wall then no work is being done. First, you have to jump up, which requires you legs doing work and your arms because they have to pull the stick up with you. At the top of your jump there is no energy in the spring. Gravity then pulls you and the pogo stick back down to the earth. Right at the lowest part of bouncing on the pavement the spring is compacted very tightly. This is because the weight of your body downward plus the acceleration due to gravity is stronger than the spring and the spring gives way. On your way back up the spring uses it's restoring force to give you an extra boost upwards. It may not help you that much, but if you go very far on a pogo stick you'll be thankful you have a spring on it.

The pogo stick works to provide young kids with hours of fun. People probably don't think about how many forces go into operating such a simple toy. However, if you really want to know how something works it is essential to break the forces down. There are all kinds of forces that participate in everything we do. Studying these forces, how they work, and what they do is essential to understanding physics. The overall idea of the pogo stick is to allow kids to jump up and down without their feet touching the ground. The spring as simple as it may seem provides a boost for you and the pogo stick on your way back up.