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| Sunday, 30 April 2006 |
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Junior Observer |  |
| News Business Features Editorial
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A great ride on the roller coaster Any child's dream is to visit Disneyland some day. Although we did not have such sophisticated activities before, Sri Lanka too is now introducing theme parks. Remember, we recently had an article about such a theme park? Anyway, when we talk about such fun activities, the roller coaster is the first thing that comes to mind. We know the experience is a little dangerous, but we still look forward to the amazement. But, have you ever thought about how these amazing machines work? If you haven't, do not worry, today we will have a closer look at roller coasters.
Roller coasters are driven almost entirely by basic inertial (property by which things continue in their state of rest or line of motion), gravitational and centripetal (moving towards the centre) forces, all manipulated (handled) in the service of a great ride. Amusement parks keep upping the standards, building faster and more complex roller coasters, but the fundamental principles at work remain the same. At a first glance, a roller coaster is something like a passenger train. It consists of a series of connected cars that move on tracks. But unlike a passenger train, a roller coaster has no engine or power source of its own. For most of the ride, a roller coaster is moved only by the forces of inertia and gravity. The only exertion (force) of energy occurs at the very beginning of the ride, when the coaster train is pulled up the first hill (called the lift hill). The purpose of this initial ascent is to build up a sort of reservoir of potential energy. The concept of potential energy, often referred to as energy of position, is very simple: as the coaster gets higher in the air, there is a greater distance gravity can pull it down. You experience this phenomenon all the time - think about going in your car or riding your bike to the top of a big hill. The potential energy you build, going up the hill, can be released as kinetic energy - the energy of motion that takes you down the hill. As we mentioned, the initial lift hill in a roller coaster serves to build up potential energy. Once you start cruising down that first hill, gravity takes over and all the built-up potential energy changes to kinetic energy. Gravity applies a constant downward force on the cars. The coaster tracks serve to channel this force - they control the way the coaster cars fall. If the tracks slope down, gravity pulls the front of the car toward the ground, so it accelerates (speeds up). If the tracks tilt up, gravity applies a downward force on the back of the coaster, so it decelerates (slows). Since an object in motion tends to stay in motion (Newton's first law of motion), the coaster car will maintain a forward velocity (speed) even when it is moving up the track, opposite to the force of gravity. When the coaster ascends one of the smaller hills that follows the initial lift hill, its kinetic energy changes back to potential energy. In this way, the course of the track is constantly converting energy from kinetic to potential and back again. This fluctuation (variation) in acceleration is what makes roller coasters so much fun. In most roller coasters, the hills decrease in height as you move along the track. This is necessary because the total energy reservoir built up in the lift hill is gradually lost to friction between the train and the track, as well as between the train and the air. When the train coasts to the end of the track, the energy reservoir is almost completely empty. At this point, the train either comes to a stop or is sent up the lift hill for another ride. At its most basic level, this is all a roller coaster is - a machine that uses gravity and inertia to send a train along a winding track. The coaster cars ride along on a long, winding track. The track begins with a steep ascent, which builds up a reservoir of potential energy in the coaster car. The rest of the track's hills, valleys, twists and turns serve to change the built-up energy back and forth between potential energy and kinetic energy. As the train moves, it gradually loses energy to friction until it reaches the end of the ride. ***** Types of roller coasters The tracks of wooden roller coasters are something like traditional rail road tracks. Wooden coaster tracks are braced (supported) by wooden crossties and diagonal support beams. The entire track structure rests on an intricate (complicated) lattice of wooden or steel beams, just like the beam framework that supports a house or skyscraper. With these materials, designers can combine the hills, twists and turns into an infinite (unlimited) variety of course layouts. They can even flip the train upside down (though this is rare in modern wooden coasters). But, since the track and support structure are so cumbersome, a wooden track is fairly inflexible. This makes it difficult to construct complex twists and turns. In wooden coasters, the motion is mainly up and down. In tubular (tube-shaped) steel coasters, the train wheels are typically made from polyurethane or nylon. In addition to the traditional wheels that sit right on top of the steel track, the cars have wheels that run along the bottom of the tube and wheels that run along the sides. This design keeps the car securely anchored to the track, which is absolutely essential when the train runs through the coaster's twists and turns. The train cars in tubular steel coasters may rest on top of the track, like the wheels in a traditional wooden coaster, or they may attach to the track at the top of the car. In suspended (hanging) coasters, the hanging trains swing from a pivoted (turn or swing from a centrally fixed point) joint, providing an additional side-to-side motion. In an inverted (upside down) coaster, the hanging train is rigidly attached to the track, which gives the designer more control of how the cars move. A tubular steel track isn't laid out in small pieces like a wooden track. It is prefabricated (manufactured in sections for assembly later) in large, curved segments, like the steel girders in a skyscraper are prefabricated. The steel manufacturing process allows for a smoothly curving track that tilts the coaster train in all directions. On a wooden roller coaster, the ride is punctuated by the rattling
sensation of the coaster rolling over the joints that connect the pieces
of the wooden track. In a tubular steel coaster, the track pieces are
perfectly welded together, making for an incredibly smooth ride. As any
coaster enthusiast will tell you, each sensation has its own distinctive
charm. |
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