Wheeee! Climb aboard Expedition Everest Disney's newest adventure ride.

Legend has it that a creature named the Yeti haunts the Himalaya Mountains in Asia. Just the mention of its name stirs fear among the villagers who live in the foothills. Nonetheless, you decide to explore the mountains, risking an encounter with the mighty Yeti.

A train takes you up a snowcapped mountain. When the train reaches the peak, its wheels halt. You see that the Yeti has ripped out the train tracks ahead. The train begins rolling backward and sends you careening through a dark mountain cave.

This heart-pounding trip is part of Expedition Everest, the newest ride at Disney's Animal Kingdom in Florida. Before you dash off to face the Yeti, meet Mark Mesko, the ride's project engineer. He tells Science World how physics helped his team of engineers create this thrilling coaster.

DREAM IT UP

Building a ride "is not as simple as saying: We'll put a piece of coaster track here or there," says Mesko. Expedition Everest is a story-driven attraction that carries "explorers" on a spine-tingling journey through the Himalayas. So Mesko's team had to think about how to use drops or turns to help convey the story line.

For example, to give riders a sense of traveling over a hilly terrain, the coaster track has many ups and downs. And to punch up the fear factor caused by the Yeti's wrath, the train tumbles down spirals. These ride elements provide thrills because they seem out of control--and they sort of are.

Most amusement-park rides--such as a carousel--are powered by onboard engines and driven by motors. "We can control the ride vehicle at any moment," says Mesko. A coaster, however, contains none of these controlling mechanisms on board. "Once you release the ride vehicle from the top of the first hill, you put things in the hands of gravity," says Mesko. This pulling force propels the cars forward (see Nuts & Bolts, 20).

UP AND DOWN

Expedition Everest is a lift-hill coaster. To get ready to surrender to gravity, its train relies on a chain to pull it up a hill. As the train climbs, it gains gravitational potential energy.

The higher it climbs, the more energy it stores. Once the train tips over the hill, gravity tugs on the coaster, sending it rolling down the track. This converts the stored energy into kinetic energy. The greater this moving energy is, the speedier the train travels.

But a coaster track contains more than just one hill. Expedition Everest has a trick-filled track that takes nearly three minutes to cross. So the coaster's engineers did calculations to ensure that each section of the track can help the train gain enough potential and kinetic energy to complete the entire ride.

One thing the engineers had to factor into their calculations was what slows a coaster down. "Friction is very important to a gravity-powered ride because it is the only thing that slows it," explains Mesko. This resisting force comes from the train's wheels rubbing against the track or the air molecules pushing against the moving train. "It takes lots of math to design a track that works," says Mesko.

ON THE RIGHT TRACK

The ride's engineers used a 3-D computer program to design a technically sound, yet story enhancing, track layout. But the track is only one part of the giant ride-design puzzle. The ride is supposed to make you feel as if you are in the Himalayas. "So we had to figure out how to package a large portion of this ride inside a mountain-like structure," says Mesko.

A creative team was responsible for designing a realistic-looking model of Mount Everest. To see if their design would look authentic, the engineers created a cardboard scale model of the track. Then, the creative team sculpted a foam model of the mountain over the track.

Oops, something didn't look right. "The track was sticking out too much at parts of the mountain," says Mesko. If the creative team altered the mountain's shape, it might not look like Everest. But if the engineers pulled in the protruding track, the calculations that kept the train moving on the track would go haywire. "The whole ride wouldn't work," says Mesko. After 23 tries, they found a track-and-mountain design that worked.

When the basic ride layout was settled, the engineers fine-tuned their calculations. For example, they determined the coaster's speed at every point on the track. If the speed at one section was too fast, the engineers figured out where to install brakes in the track to increase friction and slow the train. The team also drew the detailed technical drawings needed to build the full-scale ride.

ALL ABOARD

When Expedition Everest was finally assembled, Mesko couldn't wait to hop on. "But we had to confirm that it's safe before we put the first person on it," he says.

Instead of humans, plastic dummies were strapped into the seats. These stand-ins rode Expedition Everest as the coaster underwent extensive testing. When the system got a "thumbsup," Mesko was the first to climb on board. "It was excitement beyond belief," he says.

Nuts & Bolts

A lift-hill coaster (red) relies on a chain to pull it up the first hill. A launch. system coaster (blue), uses a thrust mechanism to boost it forward and uphill.

Once a coaster tips over the first hill, gravity propels it forward.

UP: The climbing red coaster gains potential energy (PE). The thrusted blue coaster gains kinetic energy (KE).

AGAIN: As both trains (green) climb uphill, they gain PE, but lose KE. When they roll down the turn, the trains gain and lose PE.

DOWN: As gravity pulls the red train downhill, its PE converts into KE.

DID YOU KNOW?

* Expedition Everest's ride track is nearly 1.6 kilometers (1 mile) long. The track includes a 24 meter (80 foot) drop.

* The peak of Expedition Everest's mountain structure is slightly below 61 in (200 ft) tall. Approximately 1,800 tons of steel hold up this structure. That's about six tittles the amount of steel used to build a typical office building of this height.

CRITICAL THINKING:

* Potential and kinetic energy are involved in the workings of many common machines. Think of one of these machines. Then, explain how it uses potential and kinetic energy to function.

CROSS-CURRICULAR CONNECTIONS:

ART: Have students do research on the history of amusement-park rides. Then, have each student select a ride and create a poster comparing the ride's past and present designs. Also, have students imagine and

draw what their rides may look like in the future.

RESOURCES

* The interactive feature at this Web site will help students gain a better understanding of the physics of coasters: www.funderstanding.com/k12/coaster/

* For more information on how coasters use potential and kinetic energy, go to: www.physicsclassroom.com/mmedia/energy/ce.html

DIRECTIONS: Answer the following in complete sentences.

1. How is a roller coaster different from most amusement-park rides?

2. What type of energy does a coaster gain when it climbs up a hill?

3. What happens to a coaster's energy after it tips over a hill and begins to rush down the track?

4. What slows a coaster? Where does this force come from?

5. How do brakes in a coaster track work to change a coaster's speed?

Permission granted by Science Worm to reproduce for classroom use only. Copyright [c] 2006 by Scholastic Inc.

1. Most amusement-park rides--such as a carousel-are powered by onboard engines and driven by motors. The ride vehicle can be controlled at any moment. A coaster, however, contains none of these controlling mechanisms on board. Once the ride vehicle tips over the top of the first hill, gravity takes over to propel the car forward

2. As the train climbs, it gains gravitational potential energy The higher it climbs, the more energy it stores.

3. As a coaster tips over a hill and rushes down a track, it converts its potential energy into kinetic energy

4. Friction slows a coaster. This resisting force comes from the train's wheels rubbing against the track, or from the air molecules pushing against the moving train

5. Brakes in the track help increase friction to slow the coaster.