Writing and sketching reflections playing with forces and crafting ideas from the design and iterative process of building the roller coaster.

Student Journal

Play with gravity and the forces at work on a roller coaster. Build the tracks and structure of a coaster using Strawbees straws and connectors. Then test the design with a ball to build potential energy and release kinetic energy. Explore how different iterations of the coaster structures will affect the success of the ball reaching the end.

Teacher Notes

Overview and Objectives

Materials

Facilitation and Collaboration Work

Preparation

### Facilitation and Collaboration Work

Students can read and answer questions independently or as a group.

#### Gravity in Play 

Although people may not be conscious of the fact, **gravity** is constantly at work, exerting a downward pull on all objects. There are many ordinary ways that humans experience gravity every day. Think of some of the most common activities and sports that children and adults alike play around the world.

* Football (called soccer in the United States) is played almost universally. Whether a skilled professional player or a group of children playing in a field, people can relate to the thrill of a goal, a save, or passing to a team member. None of these feats would be possible without **gravity** pulling the ball back down to the earth. 
* Children climbing hills experience the fun of **gravity** as they roll or race down the hill. 
* Skateboarders, skiers, and snowboarders gliding down slopes, jumping off ramps, and performing countless other skills and tricks, are also “playing” with **gravity**. 
* When a basketball player dribbles the ball, she propels the ball downward with both **gravity** and the force of her hand pushing the ball to the ground. Dunking a basketball can be spectacular as high leapers use force from their legs to push themselves far off the ground. While players seem to be momentarily flying above the basketball rim, each one is brought back down shortly by this force of **gravity.**

As the skier stands on top of a mountain, **gravity** is pulling downward. This helps the skier ski down the mountain.

#### Gravity in Nature 

Gravity plays an important role in nature. 

* Whether for spectacular natural phenomena like Niagra Falls or Angel falls, or any number of smaller waterfalls around the world, the power of **gravity** pulls water down from a higher altitude to a slightly lower one. 
* The moon also exerts a slight gravitational force on the earth, pulling the oceans tides up at high tide then down at low tide. The Earth exhibits a gravitational pull on the moon, which keeps the moon in orbit around the Earth. 
* Rain and other forms of precipitation free fall to the ground due to the Earth’s strong gravitational force. 
* Rock slides, landslides, falling trees, and avalanches can be disastrous because of its continual downward pull along a mountain slope.

If a tree's roots and trunk are weakened, the force of **gravity** causes it to fall down.

#### Gravity in Society

* Think of people bicycling on their way to work. To ride up a hill, people must press harder on their pedals and exert a lot of energy to overcome the downward pull of gravity. However, when they reach the top, gravity does the work for them, allowing cyclists to coast down the hill without exerting their own energy. 
* Other examples of gravity in society range from simple to complex. Irrigation and sprinkler systems rely on gravity to water fields, crops, people’s lawns, and even put out fires!  Roller coasters create an exciting experience, using gravity and speed to give a thrilling ride!

Pedaling a bike uphill requires more energy, because the biker has to overcome the downward force of **gravity**.

Warm-up

#### Relationship of Gravity to Potential Energy

Energy is the ability to do work. All things on earth and in the universe contain or use energy. Energy is constantly being transferred. One of the ways that it transfers is from **potential** energy to **kinetic** energy. **Potential** energy means that energy is stored due to an object's position or size, and the object is not actually moving yet. **Kinetic** energy is the energy associated with movement. Any moving object has kinetic energy. We play with **potential** and **kinetic** energy for entertainment, use in sports, enriching our lives. Consider a bow and arrow. An archer draws back the bowstring, creating more and more tension in the string. This tension is stored as potential energy in the arrow. When the archer releases the string, the energy immediately converts to kinetic energy, causing the arrow to fly forward. Roller coasters also illustrate just how exciting this transfer of energy can be.

#### Converting Potential to Kinetic Energy

Roller coaster cars run entirely on **gravity**, with a chain or motor to pull them up the hills. These cars resemble a train with cars connected together on a track. However, a roller coaster differs from a train in that it does not receive its power from an engine. The suspense-building, clicking sound that you hear as your roller coaster climbs has a purpose. This chain design not only pulls the roller coaster carts to the top of an incline, it also features built-in protections. When pulling the roller coaster up a hill, **potential energy** is getting stored. These coaster cars have dog chains to prevent the carts sliding backwards due to the force of **gravity** for safety. As a car safely reaches the point of a hill, **potential** energy transforms to **kinetic** energy. The safety chains let go and the cars accelerate down the hill with the aid of **gravity** and momentum.

After the chain pulls the coaster cars up the hill, the cars are full of **potential** energy. When the car begins to accelerate, the **potential** energy transforms into **kinetic** energy. The energy keeps transforming throughout the ride.

#### The Law of the Conservation of Energy

There are other forces at work on a roller coaster car besides **gravity**. Forces can make the roller coasters speed up racing down a hill, slow down when traveling up or making a turn. One of the forces acting on the cars is friction, a resistance generated from two surfaces rubbing against each other. The friction resulting from the coaster wheels against the track generates enough of this resistance to slow down. This allows the coaster cars to stay on the track, and not fall off the sharp turns. Some of the **kinetic** energy, which can also be called mechanical energy, is transformed into heat energy as a result of friction. 

Even though coaster cars slow down on turns, they maintain enough energy to complete the ride. This is due to **inertia**, another Newtonian Law, that says “objects in motion, stay in motion, unless acted on by another force.” Throughout the ride, energy is constantly exchanging from **potential** energy, to **kinetic** energy, and back to **potential** energy as it slows around turns or climbs hills.

**Potential** energy changes to **kinetic** energy, and **kinetic** energy changes to **potential** energy as a roller coaster goes down and back up hills. Some **kinetic** energy changes to thermal (heat energy) as well.

#### Design Innovation

Giant ice slides in the 16th and 17th century in Russia were precursors to the modern roller coaster. Over time, people added wheels to the sleds so that the ice slides could also be used in the summer. In the early 1800s Europeans continued to innovate these designs by adding carriages and tracks. In the United States, Josiah White built a mile and a half long track to haul coal in carts and doubled as a tourist attraction in the afternoons exhilarating visitors every day with rides reaching 50 miles per hour. Throughout the late 1800s-early 1900s, inventors continued to innovate the roller coaster with figure-eight twists, loops, and “under-friction” wheels.”  Loops did not really catch on until inventors figured out that a teardrop design was better than a complete circle.

The speed is fastest at the bottom of the hill because the cars have the most **kinetic** energy after coasting down a hill.  At the top of the hill, where the cars are slowest, they have the most **potential** energy.

#### Loop-the-loops 

For many riders, the loop-the-loop is the scariest but most exciting part of the ride. **Gravity**, **inertia**, and the track work together to make centripetal force which keeps people in their seats. Objects in motion remain in motion, according to Newton’s Laws, unless acted on by an outside force. As roller coaster passengers begin to climb the loop-the-loop, their trajectory should keep them moving forward. However, the track forces them back around and down in a sharply turning loop design. This is called **centripetal force**, and it is the force that actually keeps passengers in their seats. The passengers press down in their seat as **inertia** forces them forward.

**Centripetal** force is always pushing towards the center of the circle, and the riders are always pushing against the **centripetal** force. Therefore the forces are balanced, and the riders stay in their seats.

Imagine

#### Facilitation and Collaboration Work

For the Create section of this lesson, students can work in large groups of 3-4 building this part of the roller coaster then expanding the project even further in the [Build](#build) section.

Build pink triangle bases

Build pink sliding beams

Attach sliding beams on triangles

Make joints for top

Attach joint to close top of pyramids

Make a straight blue track

Connect both pink pyramids with track

Raise height of a pyramid by sliding beams

Make a bent pink beam

Click beam in the middle of track to straighten

Raise a pyramid to the highest height

Create

Make a blue and green triangle base

Make blue sliding beams

Attach sliding beams on the blue triangle base

Assemble joints for top locks

Attach joint to close top of pyramid

Make green sliding beams

Attach sliding beams on the green triangle base and close pyramid

Add blue tracks to the taller pink pyramid

Connect the green pyramid to tracks from pink pyramid

Connect the green pyramid to a blue pyramid with track

Construct a bent pink beam

Attach bent beam to track  and test

Build

#### Facilitation and Collaborative Work

For this section of the lesson the following questions below can be discussed all together as a class or within each group. You can use the **Student Journal** asset as a helpful resource to capture ideas and process on the computer or printed ahead of time and distributed.

Reflect

Challenges

References and Extra Resources

STEAM Classroom

United States

Use evidence to construct an explanation relating the speed of an object to the energy of that object.

NGSS

4-PS3-1

Support an argument that the gravitational force exerted by Earth on objects is directed down.

5-PS2-1

Plan an investigation to provide evidence that the change in an object’s motion depends on the sum of the forces on the object and the mass of the object.

MS-PS2-2

Develop a model to describe that when the arrangement of objects interacting at a distance changes, different amounts of potential energy are stored in the system.

MS-PS3-2

Construct, use, and present arguments to support the claim that when the kinetic energy of an object changes, energy is transferred to or from the object.

MS-PS3-5

Define a simple design problem reflecting a need or a want that includes specified criteria for success and constraints on materials, time, or cost.

3-5-ETS1-1

Generate and compare multiple possible solutions to a problem based on how well each is likely to meet the criteria and constraints of the problem.

3-5-ETS1-2

Plan and carry out fair tests in which variables are controlled and failure points are considered to identify aspects of a model or prototype that can be improved.

3-5-ETS1-3

Define the criteria and constraints of a design problem with sufficient precision to ensure a successful solution, taking into account relevant scientific principles and potential impacts on people and the natural environment that may limit possible solutions.

MS-ETS1-1

Evaluate competing design solutions using a systematic process to determine how well they meet the criteria and constraints of the problem.

Roller Coaster Run

Age range

Duration

Grades:

Topics

Assets

Roller Coaster Run