In this instructable, we're going to learn how to create the classic "game" used by carnies for decades to scam carnival goers out of their hard-earned money: the High Striker. If you aren't aware, a High Striker is essentially two parts: a lever and a puck. The puck sits on one side of the lever while the other side is struck with a hammer. The launches the puck up along a pole that guides its movement. If you hit the lever hard enough and apply enough force to the puck, it will launch high enough to ring a bell at the top of the pole.
This instructable will focus on the math and physics principles that control the High Striker, and it does not contain the actual building instructions for one of these devices. It also does not go into detail on how to adjust the machine to make it unfair. If you want to actually scam people, you'll need to figure that part out on your own.
All images within this Instructable are either my own creation or licensed for reuse under a Creative Commons License.
Step 1: Step One: Physics Concepts at Work
Before we can get into the details of how a High Striker works, there are a few principles and concepts that need to be understood.
Potential Energy: This is energy that an object has "stored" in some way. In our case, the objects (the dropped beanbag and the launched puck) will have potential energy due to gravity as they will be above the ground and able to fall. Unless something is actively resisting the pull of gravity, their potential energy will be transformed into kinetic energy as they fall. The equation for potential energy of an object is PE=(m)(g)(h), where m is the mass, g is the acceleration due to gravity, and h is the height that the object can fall.
Kinetic Energy: This is the energy of movement. It is based on the mass and velocity of a given object. If an object is not moving (velocity = 0), it has no kinetic energy. The equation for kinetic energy is KE=(1/2)(m)(v)(v), where m is the mass and v is the velocity of the object. The velocity is squared in this calculation as it contributes more to kinetic energy than mass does.
Conservation of Energy: This is one of the most important concepts in physics: energy cannot be created or destroyed, only transferred. If a ball is held still two meters above the surface of the Earth, it has potential energy. If it is released, its potential energy decreases as it approaches the ground, however, its kinetic energy will be increasing as it falls. At the moment of impact with the ground, it will have no potential energy and only kinetic energy. Due to the conservation of energy, the value of its kinetic energy at this point will be equal to the value of its potential energy right as it was dropped. While there are many kinds of energy (potential, kinetic, thermal, electrical, chemical, etc.) we will be focusing only on mechanical energy (potential and kinetic).
Step 2: Physics Concepts, Part Two
There are a few more physics components necessary to understand the function of a High Striker.
Work: Work is calculated by multiplying force times distance, and that's pretty much all it is. If you apply 20 Newtons of force to a box and push it 10 meters across the floor, congratulations! You've just done work. If you apply 20 Newtons to the wall and it moves 0 meters, you've done exactly 0 work, as the force did not cause any displacement. Work is how we describe the effort that goes into displacing a physical object.
Torque: Torque is an important part of doing work with a lever. Levers can be used to multiply a force or a distance, but only at the expense of the other factor. To put it simply, a lever can take a moderate force over a moderate distance and turn it into either a large force over a short distance or a short force over a long distance. When using a first class lever, you simply multiply one force by its distance to the fulcrum and use this value to find the unknown force/distance on the other side of the lever. Knowing all of this, torque is how we measure a force's ability to turn something. We use the torque of the beanbag falling on the lever to find the amount of force applied upward to the puck on the High Striker.
Force of Impact: When an object has some velocity (and thus some kinetic energy) and it strikes another object, this is an impact. The kinetic energy possessed by object one causes some energy to be transferred into the second object. This is essentially the force of impact. In our case, we'll be finding the force of impact when the beanbag lands on the lever. We'll be using the equation F=(1/2)[(m)(v)(v)]/d, or F=KE/d. In this equation, d is equal to the distance that the lever can travel when it is impacted.
Step 3: Given Information
Before we start doing calculations we're going to need some information about the force we will use to launch the puck. Instead of hitting the lever with a hammer, we will drop a beanbag on the lever. The beanbag will have a mass of 1 kilogram and it will be dropped on the lever from a height of one meter. The lever will be exactly one meter long, with the fulcrum placed right in the middle. The puck has a mass of 0.1 kilograms, and the lever has a mass of 1 kilogram.
Step 4: Calculations + Applications
Now, we'll walk through the calculations required to design a High Striker. See the above images for the work. Using the given information and a series of calculations, it can be found that the puck will launch 1.67 meters into the air.
It's also time to examine where the various concepts we learned about are applied.
In the first calculation, we calculate potential energy using the mass and height of the beanbag as well as gravity. The potential energy of the beanbag is 9.81 Joules.
In the second calculation, we take advantage of conservation of energy to state that the kinetic energy of the beanbag at impact will also be 9.81 Joules.
In the third calculation, the velocity of the beanbag is found to be 4.43 meters/second at impact.
Moving along to the second image, we find that the fourth calculation says the force of impact when the beanbag hits the lever is 39.42 Newtons.
The fifth calculation shows that the torque involved with our first-class lever translates the 39.42 Newtons on one side of the lever to 39.42 Newtons on the other side as well.
The sixth calculation uses the formula for work to find the velocity of the puck. It has a velocity of 5.72 meters/second.
The seventh calculation finds the kinetic energy of the puck to be equal to 1.64 Joules.
The eighth calculation again uses conservation of energy to state that the puck will have 1.64 Joules of potential energy when it reaches its maximum height.
Finally, the ninth calculation uses the equation for potential energy to find the maximum height of the puck. It will reach a maximum of 1.67 meters, which is where the bell will be placed.
Step 5: Congratulations! You're Done!
Using these calculations as a guide, you should find it easy to go out and design your own High Striker. Bear in mind that these calculations assume an ideal scenario where air resistance and friction can safely be ignored. In the real world, you'll always be losing energy to friction, so things won't perform idealy. However, this guide should be all it takes to get you started on your way to joining the proud ranks of carnival employees, shamelessly scamming your way through fairs and festivals across the country. Thanks for reading!