Technical Info Physics of a Coaster
| How a Coaster Moves | |
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If you need to know how a roller coaster moves, then you could go out and buy a rather large text book, and, upon memorizing the contents, you would be sufficiently prepared to undertake a Phd in Mechanics.
However, we don't all appreciate being forced to read through a dull textbook, and since some of you reading this will have been sent here by your physics teacher, than we can only try to dumb it down, and dare we say, make it interesting... So, the roller coaster... You've probably seen one, you may have ridden one, you may be scared of riding them, you may be obsessed with them... Whatever your opinion of the theme park's greatest asset, one thing will always remain constant: on this planet and in this dimension, at least, the rollercoaster moves as a result of gravity.
When Sir Isaac Newton felt the kiss of an apple to the noggin for the last time before he realised it was gravity that was allowing his little green chums to merrily travel downwards from the heavens and onto his awaiting head, little did he know that he was opening the door to a competitive industry fueled by his discovery. A roller coaster moves in the same way a marble would roll down a slanted surface. The marble rolls because it has Gravitational Potential Energy.  A lift hill gives the coaster "potential" energy.
Potential Energy is gathered by an object as it moves upwards, or away from, the earth. With a roller coaster, this is acheived by pulling the train up a lift hill to the coaster's highest point. As it moves higher, it has more potential to fall to earth, increasing its Kinetic Energy. Kinetic Energy is gathered as an object falls. There's a transfer of Potential Energy to Kinetic Energy as the roller coaster train leaves the top of the lift hill and enters the first drop. The more G.P.E the train has (the higher the lift hill is), then the more K.E. it will have at the bottom of the drop. This Kinetic Energy at the bottom of the drop will determine how long the ride can last for, and what elements (such as inversions or hills) the train can go through.
The ride is over, theoretically, when there is too little energy left, and the ride becomes too slow to provide sufficient thrills for its riders. However, designers almost always "cut the ride short" using brakes, due to cost, space, or capacity issues. |
| Hills and Drops |
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| The roller coaster train, having traveled down the first drop, now has a load of Kinetic Energy. There are a number of situations that could then take place. Situation 1: Flat Straight Track What a boring roller coaster this would make, but it illustrates a point. If the track after the first drop was completely flat and straight... then the Kinetic Energy would, theoretically, allow the train to continue moving forever, as energy does not disapear. In the real world, however, air resistance and friction between the wheels and the track cause the kinetic energy to be converted away, and thus eventually the train will stop. Situation 2: A Hill of Equal Height to the First Drop Another dull coaster, but this one would make the news as it is destined to get stuck. As the train speeds down the first drop, bottoms out and rises up the second hill, the train would roll back. Even though, theoretically, the train has the kinetic energy to get up the same size hill as the first drop, much of this will be lost due to friction and air resistance. As a result, the train would only make it about 3/4 of the way up the second hill before it rolls back down. Situation 3: A Hill of Less Height than the First Drop Now the train will have enough energy to get over the second hill, provided the hill is low enough to take into account the train style and weight, and continue onwards. |
| G-Forces |
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There are three forces that can be felt when riding a roller coaster, and keeping these within safe values is a vital skill for roller coaster designers. Positive G Positive G-Force occurs at the bottom of a drop as the train wants to continue moving in one direction, but the track is forcing it into the opposite direction. This can happen when pulling up at the bottom of a drop, or when going around a banked corner. The sharpness of this change from going down to going up determines the positive G. On Oblivion at Alton Towers, as the train pulls back up from the vertical drop, a massive 4.5G is exerted on riders for a brief moment.
Positive G is when you feel heavier and pressure bearing down on your body. Negative G Negative G is found at the top of hills and occurs when a train crests a hill at speed, or suddenly dips sharply downwards. Negative G is the most fun G-Force, but it is also the most dangerous. The G forces between 0 and 1 (but less than 1) G's are also often considered negative-G's. This is because at anything less than 1G, your body will experience a slight variation of the "floating" sensation you feel when you experience actual negative G's. It should be noted that the G's between 0-1 are only considered "negative-G's" in the coaster enthusiast world - in almost all official companies and industries, a true "negative-G" is only one that is less than 0G's.
Good negative G should produce awesome "willy-lift". Lateral G Lateral G-Force occurs when a train goes around an un-banked corner, or a corner not banked far enough. Riders bodies are jerked sideways and this is why Wild Mouse rides are so painful. Most high speed roller coasters will have banked corners, which prevent or lessen lateral G and convert it to positive G.
Lateral G will leave your sides bruised. Linear G Linear G is found during a coaster that launches in a straight line very quickly. Linear G-Force is fun, and the limit has not yet been reached on a roller coaster. Kingda Ka exerts high linear G as it accelerates from 0 to 128mph in around 3.5 seconds. Linear G is what pushes against your face during high-speed launches (not to be confused with the air that you are being launched into). |
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