Yerxa, STEM/EDP Wheel, Grade 8Period 4

Part 1 (of 3): 4/20 & 4/22Newspaper Roller Coaster Design Challenge

For this engineering design challenge you will be asked to engineer a new, thrilling rollercoaster. But before getting started with the challenge you need to learn about how rollercoasters work. Week 1 you will learn about the Science behind roller coasters & Week 2 you will design and build your rollercoaster.

1st - Complete the K (Know) before reading section of the K-L Chart below (Mon. 4/20)

K-L Chart RollercoastersStatement Before

ReadingAfter

ReadingEvidence

(explain the correct answer)

agree disargree agree disargree

1. At the bottom of the hill, a roller coaster has the greatest amount of potential energy.

2. If you are experiencing “1 G-force” you feel weightless.

3. Roller coasters work by converting potential energy into kinetic energy and visa versa.

4. Potential energy is the energy of motion.

5. Inertia makes your body push into the side of a car when the car turns sharply.

6. When you travel in a loop you don’t fall out because of gravity.

7. Energy is never created or destroyed in a roller coaster. It just recycles.

8. Friction between the track and car causes the coaster to slow down.

9. Centrifugal force is caused by gravity and keeps you from falling out of the car when go

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through a loop.10. The coaster has it’s

maximum amount of energy when it starts and is at the highest point of the hill. Even newer rollercoasters.

11. Your stomach drops when you go down a hill in a rollercoaster because of inertia.

12. It is best to ride in the front of a coaster if you want to get whipped around quickly.

2nd – Reflect on your past experiences: Have you been on a rollercoaster before? How does it make you feel or your body move when you: (Mon. 4/20)Action (what the coaster

does?)Reaction (how do u feel/move?)

When it is pulling you up hill

When you drop down a hill

When you come back up a hill

When it makes a sharp turn right

When you go around a loop

When you stop abruptly

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How Roller Coasters Work Reading (Mon. 4/20 & Wed. 4/22)We can’t all be reacing drivers or astronauts. Not everyone can dive to the bottom of the sea or climb up Mount Everest. But we can all go on rollercoasters and see what it feels like to push ourselves to the limit. You might think rollercoasters are all about testing your body, but your mind’s being worked out too: the mental psychology of fear makes the whole physical experience so much more exciting. Lets take a closer look at the science of extreme rides.

Energy in a rollercoaster rideHave you ever wondered why rollercoaster cars don’t have engines? Vehicles don’t always need that kid of power to make them go. But they do need energy of some sort. Before a rollercoaster ride begins, electricity from an electric winch pushes the car to the top of the first hill. That can take a while, because some rollercoasters start off nearly 330 feet in the air!

If you remember the law of conservation of mass states that energy is never created or destroyed. It is just recycled into different types of energy; solar energy, mechanical energy, electrical energy, thermal energy, nuclear energy, chemical energy, and light energy. Rollercoasters use this law by converting energy to different types to make a fun ride.

But the energy of a rollercoaster has to start somewhere. The rollercoaster has a winch (something that winds up a cable) that is tied to the rollercoaster car. The wench has to use energy from electricity to pull the rollercoasters up the hill. But that energy doesn’t simply disapper. The rollercoaster cars store it just by being up in the air – and the higher up the car is lifted, the more energy it stores. It will use energy from this to race back down the hill when the ride begins. Because they have the ability (or potential) to use in the future energy that was stored in the past, we call the energy they’re storing potential energy.

Once everyone’s onboard and at the top of the hill the cars, which now have gravitational potential energy, are released and start to roll down the track. Once they round the first hill, the force of gravity makes them hurtle downwards, so they accelarate (pick up more and more seed). As they accelerate, their potential energy turns into kinetic energy (the energy things have because they are moving). The word “kinetic” comes from the Greek word meaning to move. The faster the car moves the more kinetic energy is produced. The greater the mass and speed of an object, the more kinetic energy there will be. As the car accelerates down the hill it moves faster and the potential energy is converted into kinetic energy. There is very little potential energy at thebottom of the hill, but ther is a huge amount of kinetic energy.

What goes up must come down! At the start of the ride, the cars has a certain amount of potential energy. The kinetic energy that makes a rollercoaster car speed up comes from the potential energy the car gained when it was hauled to the top of the first hill on the ride. They can never have any more energy than this, no matter how long the ride

Winch

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lasts. Throughout the ride, they are constantly swapping back and forth between potential and kinetic energy. Each time they race up a hill they gain more potential energy (by rising higher in the air), but they compensate for it by losing some kinetic energy too (by slowing down). That’s why rollercoaster cars always go slower in the higher parts of a ride and faster in the lower parts.

In theory, this process could go on forever and the ride would never end. But in practice, some of the potential energy the cars started off with is constantly being used up by friction, when the metal wheels rub against the track. Air resistance pushing against the front of the car when it moves takes away more of the energy as well. Even the rattling noice the rollercoaster makes uses up some of it’s energy. If the curves aren’t perfectly shaped, the cars loose even more energy. The cars lose more and more of their original energy the longer the ride continues, and, since the cars have no engines, there’s no way of replacing it. That’s why the loops on a rollercoaster ride always get smaller and smaller. It’s why rollercoaster rides must always come to an end sooner or later. The cars simply run out out of energy (see picture above).

Law of Conservation of MassDefinition (in own words): Picture (applied to a rollercoaster):

Potential EnergyDefinition (in own words): Picture (applied to a rollercoaster):

Gravity & AccelerationDefinition (in own words): Picture (applied to a rollercoaster):

The forces that act on a roller coaster

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Kinetic EnergyDefinition (in own words): Picture (applied to a rollercoaster):

Forces in a rollercoaster ride (Wed. 4/22) Energy is what makes a rollercoaster ride last, but forces are what makes it so thrilling. You can’t see the forces pushing and pulling your body as you race round the track. But it’s forces that knock you backwards. It’s forces that make you feel as light as air one minute and as heavy as a rock the next. It’s also forces that keep you safely in your seat whe you suddenly spin upside down.

Wherever you are in the ride, lots of different forces are always acting on your body. The biggest force you feel is your weight – and the weight of the cars and the other people on the ride. All that weight doesn’t simply pull you straight down. It pulls you forward when race down a hill and backwards when you climb. This weight is due to gravity. There are other forces at work too. Air resistance pushes against your face and limbs and is caused because the air is pushing against you the faster the car goes. There’s also a friction force between the metal car wheels rubbing on the metal track. And because you push down on the car seat with your body, the metal track pushes back on your car, which rubs and slows the car down even more. All these forces acting on you are never quite in balance – that’s why you zoom down the track, whey the car rattles and why you shake about so much. In order to understand how to create a roller coaster that is thrilling, you need to understand Newton’s 3 laws.

From moment to moment, the forces you feel are never the same – and that’s why the ride is so unpredicable and exciting. Much of this is due to Newton’s 1st law of motion (A.K.A. Law of inertia), which says that a body in motion will stay in motion unless a force acts on it. The riders, which have inertia, are acted on by unbalanced forces throughout the ride causing them to change their motion. When a force acts on you, your body will fight the force. So, when you are moving forward in the car and the car turns to the left, your body will continue to go straight even through the car is turning to the left. This makes your body feel like it is being pushed right and away from the turn. It is your inertia that resists the change in directional motion. When you do a loop-the-loop, the direction you’re moving in is always shifting. That means the forces you feel are also changing from one second to the next. Before coming into the loop, you bairly feel any force at all. As you start to climb, you feel an enormous force dragging you backwards. The force gets stronger and stronger. At the top of the loop, you feel like you’re going to fall out of your seat but it is your inertia that holds you in. Your body is sitting in the car, which was going straight, but when you hit the loop and begun to go up your body’s inertia resisted the upward movement and pushes out. Inertia is why your body does not fall out of the car when you go through a loop. This inertia that acts outward

Newtons 1st Law (Inertia)

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(from the circle) on your body that is moving in a circle is called centrifugal force. The force gradually gets weaker again as you come back round to the straight. On the other hand, inertia might even throw a passenger from a car even, but thankfully, the safety bars act on the riders too and holds them in their seats.

In order to get a car to go go fast and accelerate, you must understand Newtons 2nd law of motion, which states that force = mass X acceleration. You feel Newton’s second law when you start to go down the hills. Coaster cars and your body have mass. Gravity exerts a force on that mass, which can then cause it to accelerate. The rider feels that force as one moves along the coaster track. The mass of the cars and you body are constant and remains the same from start to finish. The amount of force a rider experiencesl varies only with the acceleration of the cars along the track. As the roller coaster speeds up (positive acceleration) racing downhill or turning abruptly, the amount of force a rider feels increases. As the roller coaster slows down (deceleration) due to friction between the wheels and the track or air rushing by, the forces a rider feels ease off. Variables an engineer might consider to change the force experienced by the rider include, starting the car really, really high (adding gravitational potential energy), added loops and sharp turns, or increasing the mass of the cars. All theses variables fall into the category of acceleration or mass when calculating the force experienced by a rider.

You have to wear a safety harness to keep you in your seat because the forces on rollercoaster rides are so extreme. But thats all part of the fun. According to Isaac Newton’s 3rd law of moton, for every action there is an equal but opposite reaction (action-reaction), so when you press against the seat restraints, they press back on your body. And when you are being pushed down, the seat is pushing back at you. This law comes into play with newer roller coasters that expose riders to high G-forces. “G-forces” relate to the acceration on a body due to gravity (G). Gravity exerts a force of 32 feet/sec.2 (1 G-force) on your body even when you are sitting down. What happens to your body in a 2 G-force turn? Your body accelerates so rapidly that it experience forces twice that of the normal force of gravity. The biggest force comes when you’re just starting to move down a hill. This is when you feel your stomach drop because your G-force increases. The force is lowest in the dips between the hills. (Your speed is in exactly the opposite pattern: it’s lowest when you’ve just gone over a hill and highest in the dips beteen hills.) Older coasters did not expose riders to very many G-forces as they relied only on the force of gravity to accerate riders. Newer coasters may catapult, sling or use hydraulic or jet forms of propulsion to accelerate riders along faster and faster. These newer coasters have created exciting ways to create action, which in turn you, the rider, experiences as a reaction on your body.

Centrifugal Force

G-forces

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The forces you feel also depend on whereabouts in the train of cars you’re sitting. If there are lots of cars and the train is quite long, different cars can be at different points on the ride. The front cars may be racing down a hill while the back cars are still climbing up behind them. All the cars are coupled together, so the front cars pull the back ones along at the same speed. But the forces on people sitting in different cars can be quite different. When the front car goes over a hill, it’s bairly even moving. Sometimes it goes so slowly you wonder if it’ll even get to the top. Then, as it starts racing down the hill it pulls the other cars along behind it. When the back of the car starts climbing a few seconds later, it’s whipped over the top really quickly – and you almost fly out of your seat. As the back car races over the hill, you feel weightless (or 0 G-force) for a second or two. That’s why, for sheer exhilaration, the back car is often the best one to sit in. If you like a good view, though, sit in the front.

Friction is a force that opposes the motion of an object. If the roller coaster cars are moving left, the friction is to the right. The force of friction acts on the moving cars, decreasing the total amount of mechanical energy (a combination of potential and kinetic energy) on the rollercoaster. The mechanical energy is not lost, however. It is transformed into thermal (heat) energy, which can be detected as an increase in the temperature of the metal roller coaster track and car wheels. Because of friction between the coaster cars and the track, and let’s not forget air resistance as the cars move forward, the amount of mechanical energy available decreases throughout the ride, and that’s why the first hill of a roller coaster must be the tallest. The force of forward momentum slowly decreases throughout the ride. At the end of the ride friction between the wheels and the track or wheels and their brakes slowly wins out and the cars come to a hault.

All those forces pushing you in one way and the other only add to the enjoyment – until it comes to an end!

Newton’s 1st Law of Motion (Inertia)Definition (in own words): Picture (applied to a rollercoaster):

Newton’s 2nd Law of MotionDefinition (in own words): Picture (applied to a rollercoaster):

Newton’s 3rd Law of Motion (Action-reaction)Definition (in own words): Picture (applied to a rollercoaster):

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FrictionDefinition (in own words): Picture (applied to a rollercoaster):

Reflection (Wed. 4/22)1. NOTE : Now go back up to the K-L Chart and complete “After Reading” and

“Explanation”.Recycling Energy

2. Energy is never created or destroyed – it just recycles. Match each type of energy w/ each statement below:Potential energyKinetic energy

Thermal (heat) energy

Electrical energyMechanical energy

The winch pulls the coaster to the top of the hill.

The coaster reaches the top of the hill & is waiting to go down.

The coaster is accelerating down the hill & up & around the loops.

Friction between the metal coaster wheels & the track rub & heat up, which slows the coaster down.

A roller coaster moves because it transfers between potential & kinetic energy.

3. Label the parts of the roller coaster below:Potential energyKinetic energyMechaical energy

Centrifugal forceFrictionInertia

Electric energyZero (0) G-force

1.2.3.4.5.6.7.8.

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