How Things Work: Roller Coasters

Jun Xian Leong Apr 15, 2007

Roller coasters are truly a lesson in physics, as most roller coasters involve momentum, inertia, and gravitational acceleration, with outside propulsion provided only at the very beginning of the ride.

The concept of a roller coaster began with Russian ice-slides, which were tall platforms built during winter with a long ramp coming down on one side. People would then cover the ramp with a layer of snow, and “sliders” could climb up the ladders on one side and slide down the snow-covered side on large sleds.

By the year 1817, Les Montagues, the first roller coaster with cars that locked onto rails, was built in France, and roller coasters have been a source of wild excitement worldwide ever since.

Even today, roller coaster cars are, essentially, little more than sleds with wheels. The basic car does not contain any electronics or motors, and sometimes, does not even have brakes. The car is towed up the initial incline by means of an external conveyor, or sets of motored gears. From thereon out, though, it’s pure physics at work.

Potential energy is stored as the cars are towed up the first incline, reaching a maximum as the car arrives at the top. As the car goes over the peak, gravity accelerates the car down the incline.

This acceleration is a conversion of potential energy to kinetic energy, meaning that the car accelerates. The car gains speed and momentum as it rolls down the hill, and this built-up momentum is all that propels the car around the bends, loops, and twists that make riding a roller coaster an exciting experience.

By the laws of conservation of energy and momentum, however, the total energy of the car cannot exceed the initial given energy. Hence, the first hill must always be the highest, and each subsequent hill cannot exceed the height of the one before it if the car is to successfully go over the peak.

Furthermore, friction and other dissipative forces cause the car to constantly lose energy to its surroundings in the form of heat and sound, and this means that each hill must be strictly lower than preceding ones.

The concept is similar to that of a ball rolling down a hill. As long as the overall incline of the hill is downward, the ball will continue to roll down, even if it encounters bumps that launch it upward at times.

The first public roller coasters were constructed out of wood, and even today, many of these wooden roller coasters remain in use worldwide.

Wood is a much weaker substance than steel, however, and wooden roller coasters cannot hope to match steel coasters in terms of height, incline steepness, and track length. Most wooden roller coasters do not have loops.

Steel roller coasters were not widely built until the mid-1900s. However, the beginning of steel roller coasters marked an entirely new age in roller coaster construction. Steel is much stronger and more malleable than wood, and it allowed for the creation of loops, corkscrews, and other features that are commonly seen in modern roller coasters.

Among some of the most important things that designers must pay attention to when designing a roller coaster are the acceleration, the rate of change of acceleration — “jerk,” and the rate of change of jerk — “snap.”

The acceleration is extremely important in determining if a ride will be exciting and sufficiently scary without being uncomfortable. “Jerk” and “snap” measure the forces present upon various parts of the coaster at each point in its movement, and are pivotal in roller coaster safety.

Maintaining reasonable levels of “jerk” and “snap” ensure that neither the users nor the building framework are subjected to abruptly large forces, which could cause bodily harm or structural collapse.

Today’s most modern roller coasters incorporate many new features, including accelerator pads midway to prolong the ride and reversible tracks through which cars travel both ways during a single trip.

Furthermore, improved methods of propulsion such as magnetic accelerators or compressed air launcher systems are currently being used to launch roller coaster cars up to speeds of 100 miles per hour in a few seconds, and the highest roller coasters in the world can tower up to over 400 feet high. The Kingda Ka at Six Flags in New Jersey, for instance, drops 418 feet and is accelerated to a maximum speed of 128 MPH in just over 3 seconds.

Neurologically, because a roller coaster is thrilling, it triggers the fight or flight response within the human nervous system by presenting it with situations perceived to be dangerous. This induces the release of adrenaline and dopamine in the brain, which acts as a “reward” for having survived. Hence, the more dangerous a coaster seems to be, the greater the rush one gets from riding.

Because they are built to simulate dangerous situations, roller coasters are built under the strictest regulations possible for the safety of the users. Six Flags conducted a study in which researchers found that there is a less than one in one-and-a-half billion chance that a rider will be killed from injury.

Roller coasters are truly a lesson in physics, as most roller coasters involve momentum, inertia, and gravitational acceleration, with outside propulsion provided only at the very beginning of the ride.

The concept of a roller coaster began with Russian ice-slides, which were tall platforms built during winter with a long ramp coming down on one side. People would then cover the ramp with a layer of snow, and “sliders” could climb up the ladders on one side and slide down the snow-covered side on large sleds.

By the year 1817, Les Montagues, the first roller coaster with cars that locked onto rails, was built in France, and roller coasters have been a source of wild excitement worldwide ever since.

Even today, roller coaster cars are, essentially, little more than sleds with wheels. The basic car does not contain any electronics or motors, and sometimes, does not even have brakes. The car is towed up the initial incline by means of an external conveyor, or sets of motored gears. From thereon out, though, it’s pure physics at work.

Potential energy is stored as the cars are towed up the first incline, reaching a maximum as the car arrives at the top. As the car goes over the peak, gravity accelerates the car down the incline.

This acceleration is a conversion of potential energy to kinetic energy, meaning that the car accelerates. The car gains speed and momentum as it rolls down the hill, and this built-up momentum is all that propels the car around the bends, loops, and twists that make riding a roller coaster an exciting experience.

By the laws of conservation of energy and momentum, however, the total energy of the car cannot exceed the initial given energy. Hence, the first hill must always be the highest, and each subsequent hill cannot exceed the height of the one before it if the car is to successfully go over the peak.

Furthermore, friction and other dissipative forces cause the car to constantly lose energy to its surroundings in the form of heat and sound, and this means that each hill must be strictly lower than preceding ones.

The concept is similar to that of a ball rolling down a hill. As long as the overall incline of the hill is downward, the ball will continue to roll down, even if it encounters bumps that launch it upward at times.

The first public roller coasters were constructed out of wood, and even today, many of these wooden roller coasters remain in use worldwide.

Wood is a much weaker substance than steel, however, and wooden roller coasters cannot hope to match steel coasters in terms of height, incline steepness, and track length. Most wooden roller coasters do not have loops.

Steel roller coasters were not widely built until the mid-1900s. However, the beginning of steel roller coasters marked an entirely new age in roller coaster construction. Steel is much stronger and more malleable than wood, and it allowed for the creation of loops, corkscrews, and other features that are commonly seen in modern roller coasters.

Among some of the most important things that designers must pay attention to when designing a roller coaster are the acceleration, the rate of change of acceleration — “jerk,” and the rate of change of jerk — “snap.”

The acceleration is extremely important in determining if a ride will be exciting and sufficiently scary without being uncomfortable. “Jerk” and “snap” measure the forces present upon various parts of the coaster at each point in its movement, and are pivotal in roller coaster safety.

Maintaining reasonable levels of “jerk” and “snap” ensure that neither the users nor the building framework are subjected to abruptly large forces, which could cause bodily harm or structural collapse.

Today’s most modern roller coasters incorporate many new features, including accelerator pads midway to prolong the ride and reversible tracks through which cars travel both ways during a single trip.

Furthermore, improved methods of propulsion such as magnetic accelerators or compressed air launcher systems are currently being used to launch roller coaster cars up to speeds of 100 miles per hour in a few seconds, and the highest roller coasters in the world can tower up to over 400 feet high. The Kingda Ka at Six Flags in New Jersey, for instance, drops 418 feet and is accelerated to a maximum speed of 128 MPH in just over 3 seconds.

Neurologically, because a roller coaster is thrilling, it triggers the fight or flight response within the human nervous system by presenting it with situations perceived to be dangerous. This induces the release of adrenaline and dopamine in the brain, which acts as a “reward” for having survived. Hence, the more dangerous a coaster seems to be, the greater the rush one gets from riding.

Because they are built to simulate dangerous situations, roller coasters are built under the strictest regulations possible for the safety of the users. Six Flags conducted a study in which researchers found that there is a less than one in one-and-a-half billion chance that a rider will be killed from injury.