When Sir Isaac Newton first felt an apple bounce on his head, the theory of roller coaster motion was born

When a rider is on a coaster, Newton’s Law of Motion is probably the last thing on their mind, but every element of the physical thrill of the ride depends on physics

A coaster moves in the same way a marble would roll down an inclined surface

Potential Energy is accumulated by an object as it moves up, or away from, the Earth

A coaster train gains potential energy as it is pulled up a lift hill to its highest point; The train has a higher potential energy

The lift hill gives the coaster “potential” energy

When an object falls back to Earth, it collects Kinetic Energy

The transfer of Potential Energy to Kinetic Energy occurs when the roller coaster exits the top of the lift hill and descends on the first drop

The greater the potential energy in the train accumulated during the climb up the lift hill, the more kinetic energy the train will have at the bottom of the roll

Coaster rails control the angle of descent meaning that the steeper the first drop, the greater the kinetic energy

The kinetic energy at the bottom of the roll determines the distance the coaster train can travel along the track and through inversions, banked turns and airtime hills

The calculation between the lift hill and the drop height must be precise, otherwise the train will not collect enough potential and kinetic energy to complete the circuit

Coaster designers then have to consider what happens after the first drop

If the track after the first roll is completely flat and straight, the kinetic energy will, in theory, allow the train to keep moving forever, since no energy is lost

However, in the real world, air resistance forces and such friction between the wheels and the track dissipate kinetic energy

The train would stop moving without any kinetic energy

Condition 2: Elements with the same Height as the First Drop

In this situation, when the train accelerates down the first drop and climbs up the second element, it will roll again

Although, theoretically, the train has the kinetic energy to go up the hill of the same size as the first roll, some of the kinetic energy will be lost again due to friction and air resistance

The train will only go about 3/4 of the way up the second hill before rolling back down

Condition 3: High Element Less Than First Drop

Providing the element after the first drop is low enough to take the weight of the train into consideration, this is the perfect situation to allow the coaster to continue to the next element

Several forces are felt when riding a coaster, and keeping these at a safe value is an important skill for coaster designers

G stands for Gravity and the number in front of it indicates how many times the force of gravity is felt at a given point

If the theme park says the coaster rider will experience, for example, 4G, the rider will experience four times the force of gravity

G Forces create the air time that riders experience

Ejector Airtime is where the rider feels like they are being ejected quickly from the coaster

Floater Airtime is a smoother sensation where the rider feels weightless

Positive G-Force occurs at the bottom of a roll when the train wants to keep moving in the same direction, but the track forces it in a different direction

Positive G forces usually occur on turns or when a train pulls up a hill after going down

For example, in Oblivion at Alton Towers, when the train reverses from a vertical drop, a massive 45G is applied to the riders for a moment

Positive G is when the rider feels heavier as the pressure drops, as if being pushed down into the seat

Negative G is usually experienced when a train is going up a hill at high speed, or suddenly going down a hill

Negative G is considered the most exciting but also the most dangerous G Force

Negative force is measured between 0 and >1 G

Anything less than the standard 1G force is considered weightless and causes the sensation of floating

A good negative G should produce a weightless floating sensation

Lateral G forces occur when a train goes around a corner without a bank, or a corner that is not far enough away

This is usually experienced when the rider is suddenly forced sideways, as in the flat hairpins found on the Wild Mouse coaster

Most high-speed coasters contain banked corners, which prevent or reduce lateral G and convert it into positive G

Lateral G pushes the rider to one side

Linear G occurs when the coaster is launched at high speed in a straight line

The human body can tolerate high levels of Linear G forces

The Kingda Ka at Six Flags Great Adventure provides high linear G while accelerating from 0 to 128 mph in about 35 seconds

Linear G forces propel the rider during a high-speed launch

The Linear G force riders returned to their seats

Human Tolerance and Safe Limits

Positive G Head to Foot is denoted by +gz

Negative G’s Foot to Head is denoted -gz

Linear G’s Back to Chest is denoted -gx

Linear G’s Back to Chest is denoted -gx

Lateral G from Left to Right is denoted -gy

Lateral G from Left to Right is denoted -gy

Positive G-Force Tolerance

The human body can usually tolerate about +9gz with the help of protective settings

Positive G-Forces become uncomfortable for the human body at +5gz

At 1gz, humans show no adverse effects other than gradual aging as this is the natural rate on earth

When in high positive G, blood is forced from the head to the feet so that the rider “grays out”

Negative G-Force Tolerance

The human body shows alarming symptoms at only -2gz and in coasters a level higher than -1gz would be considered dangerous

At -1gz, humans show a sense of pressure in their heads

When in high Negative G, blood rushes to the head and can cause very serious organ problems ‘Red Out’ and cause the brain to bleed

Linear G-Force Tolerance

Lateral G-Force Tolerance

Humans can tolerate high levels of lateral G if properly restrained; Otherwise, injury to the body may occur

Scroll to Top