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Roller coasters, & ball runs with K'Nex


This page includes sample investigations with coasters and ball runs. While K'Nex are the construction materials for most of the examples other materials may be substituted. For clarification I refer to any track that completes a circle as a coaster and one that does not as a ramp. Also there are two kinds of vehicles. One where the wheels ride on top of a ramp and a coaster vehicle with two sets of wheels so one wheel rides above and the other below the rail, with the rail in between.

Many kinds of investigations can be made to explore the science of coasters and ball runs, as well as team building and cooperative learning activities with K'Nex. In these activitied learners may use K'Nex to building coasters or runs and explore differerent variables to discover how they affect the motion or ride. Concepts can include:

May use K'Nex ® to create a down hill ramp, ball run or a circular run (coaster) to explore motion, force, and mass. Create a ramp; roller coaster; or ball, marble, or sphere run; where an object (marble or vehicle) will travel the entire track. Samples ...

The K'Nex ® set Down hill thrill includes a track with a jump and one with four drops the Devil's Drop course. The hill below was used for most investigations with the jump removed and more track added for a horizontal run.


Serpent coaster set models


More designs

Coaster with loop

Coater with loop

Coaster with loop

Coaster with loop

Coaster straight run

Straight run coaster

Coaster with spiral

Coaster with spiral



Ramps are great, but coaster take it to another level.

Why coasters?

Roller coasters have been around for over 100 years and they are still as popular as ever. Amusement parks all over the world are compete for riders thrills and money. But all coasters have one thing in common. The first hill on every coaster is the tallest hill on the ride. Why? Besides to build suspense for the upcoming drop!

If you study what is happening on that first hill, the coaster is being pulled up to the top of the hill by a strong motor and chain. But at the top of the hill the chain disengages and the coaster coasts down the hill and up, over and around the rest of the track. To coast around the entire track the coaster requires a lot of energy. The energy comes from the work the motor does to pull the coaster cars to the top of the hill. The motor received its energy from either electricity or gasoline depending on its type. At the top of the hill this work from the motor has been transformed into an increase in the coaster car's potential energy. Energy which is stored and can be used later. It comes from the object's height from the ground. As the cars move downhill, the energy becomes kinetic (motion) energy.

Of course, the ride is not all downhill. As the coaster glides over the hills and through the loops, the energy converts back and forth between kinetic energy and potential energy. A coaster can never go as high (or as fast) as it does on the first hill, because of friction between the wheels and the steel track. This friction robs some of the coaster's kinetic energy and transforms it into heat. Since no additional energy is given to the coaster, the loss of kinetic energy prevents the coaster from climbing any other equally tall hill. This is an example of one of the greatest generalizations in science, the law of conservation of energy, which states: Energy cannot be created or destroyed; it may be transformed from one form into another, but the total amount of energy never changes.

Therefore at any point of the ride, if you totaled the potential, kinetic, heat, and sound energy (plus any energy you, the track, or the air may absorb) their total would equal the original amount of energy the coaster had at the top of the first hill. As the coaster goes down the first hill some of its energy is transformed into other forms which leaves less kinetic energy available to get it up the next hill. So the next hill must be smaller than the first or the coaster will not go over it.


Focus questions


Select a focus question or two for big ideas to investigate. Decide on what kind of system to use to explore and investigate. Review information below to plan and write a sequence for an investigation. What to explore and how, data to collect from the exploration, and questioning strategy to answer more specific questions to invent scientific concepts and to apply them to more investigations and explain what is happening and why.

Planning information by categories ...

Energy - potential and kinetic

Energy is a tough concept to understand and explain because the only time it can really be seen, felt, or heard is when it is being transferred from one form to another or being transported from one place to another. For us to concretely observe the effects of energy, something has to happen. Ramps, ball runs, and coasters can be used to illustrate and help learners discover the concept of energy.

Background information

Energy is defined as the ability to do work. And work is the ability to apply a force (push or pull) over a distance. (A fourth grader accurately defines energy as: something that makes things move. An underlying functioning of every coaster is a basic law of physics: the law of conservation of energy. This fundamental law of physics has nothing to do with saving energy but what happens to energy when it is used. The law states that energy cannot be created or destroyed; it may be transformed from one form to another, but the total amount of energy never changes.

The learners energy is used to do work on the vehicle or sphere when it is placed at its starting point on the track. The energy is not lost, but transferred to the vehicle. The vehicle now has a higher energy level due to its higher position off the floor. This is called potential energy. The higher it is raised, or the heavier it is, the higher its potential energy. When it is released, the potential energy transforms into energy of motion or kinetic energy. At no time can it have more kinetic energy than its original amount of potential energy. Throughout the coaster ride it experiences a continual interchange of potential and kinetic energy as it rolls over the hills and through loops. But at no time will the combination of the two be greater than the initial amount of potential energy at the starting height of a ramp or starting hill if the coaster is lifted from a starting point to the top of the initial hill.

Focus questions


Coaster energy challenge

Review the diagram and answer the questions about the energy at different positions.

Roller coaster puzzle for kenetic and potential energy

  1. How does the potential energy of the car on the roller coaster at position
    • A compare to that at B?
    • B compare to position C?
  2. What affect does the loop have on
    • the potential energy of the car?
    • Its kinetic energy?
  3. How does the kinetic energy of the car at postion
    • A compare to B?
    • B compare to position C?

Place an X on the point where the kinetic energy is the greatest.

Identify where the kinetic energy is the lowest.

  1. If the car's weight were decreased by a large amount, how would the potential energy, kinetic energy and the distance of run be affected?
  2. If the car's position were increased to a height of 40 meters, how would the potential energy, kinetic energy and distance of run be affected?


Motion, curves, forces & Newton’s laws

Newton’s first law says that an object in motion will keep moving at the same speed in the same direction unless a force is applied.

So according to Newton’s first law, if direction changes there needs to be a force.

Newton’s third law is, for every force there is an equal and opposite force. Or, if a force acts on an object, the object also exerts a force.

Vertical curves.

Science process and perspectives



Dr. Robert Sweetland's notes
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