The Thrill behind Amusement Rides: Acceleration and physical effect

Abstract.

This paper looks specifically at gaining a clear and concise understanding of the physics principles behind the development of amusement rides, with a focus on acceleration and physical effects. The purpose is to provide background, evidence and examples of such physics and their effects on the guests. It will provide theory, examples, pictures and on-site practical measurement evidence in support.?By verifying the data, and combining such evidence, we can provide an introductory insight into these aspects of amusement rides for consideration by professionals new to this field.

Introduction.

Professionals new to working in the amusement ride industry often have many questions that may go unanswered. For example; why is there an age and height limit for the ride? How can we improve the thrill experience for the guest? What controls the safety requirements for rides? What are the physics principles behind the movements of rides?

The purpose of this article is to examine and offer some clear explanations to questions that are directed towards the physical effect on the guest when they experience different amusement rides inside a family entertainment centre.?

In order to understand these effects on the guests, we also must understand some of the complexities of physics. Such complexities, terms and laws are not only related to the particular industry in question but originate in the fundamentals of gravity perception, space science and biomechanics.?

This article will start by stating the clear and concise explanation of microgravity, different types of motion, biomechanics and the effects of acceleration. It will also reflect on Newton’s Law of Motion, with rationale exemplified by a small study of the subject area in question.?

Gravity & Microgravity

Gravity is a natural phenomenon that is always present between any two objects with mass, attracting them together (These two objects can be stars, galaxies and other).

Earth’s mass creates a gravitational field that attracts objects with a force inversely proportional to the square of the distance between the centre of the object and the centre of Earth.?

Our weight is the gravitational force of the Earth acting on our bodies.?

Ignoring air resistance, it was discovered by Galileo that everything on Earth falls at the same rate of 9.81 meters per second of velocity due to the gravitational force of Earth which is, in other words, the gravity of the Earth - ?g = 9.81 m/s2.

Microgravity signifies the condition in which people or objects appear to be weightless.

The best example for microgravity can be seen when astronauts float in space.

Microgravity is the difference between acceleration and ‘g’ in different parts of a spaceship. This ‘difference’ can be created on the ground.

The motions created by a roller coaster change the apparent weight of the guest which creates a similar feeling to the astronauts in the spaceship.

??In most science fiction movies, artificial gravity is given as there should not be the issue of microgravity inside spaceships. This can be provided, scientifically, by accelerating the spacecraft at 9.8 m/s2 and invoking Einstein’s equivalence principle.?

Motion types and measures

Motions can change the effect that acceleration has on the body, enough to create a microgravity environment.

To simplify the rides classification, there are three types of motions monitored in amusement rides. These can be found individually or combined depending on the design of the ride. They are as following.

Linear Motion:?This is when an object, or ride, moves in a straight line. Bumper cars move in a horizontal linear path whereas free fall rides have a vertical linear motion.

Curved Motion: This is when an object, or ride, moves in a curved motion. The traditional roller coaster is a combination of horizontal and vertical linear motion as well as curved motion.

Circular Motion: This is when an object, or ride, moves in a circular motion. This can be seen in a pendulum ride like Skate 360, Twist and Swing or the traditional Ferris wheel.

These different types of motions are fundamental in the physics of the amusement ride.?It is therefore important to understand how these types of motion are measured.

There are three important elements to measure the motion of the ride.

1-???Displacement: when the ride changes the position.

2-???Velocity: how fast the ride is at any given moment.

3-???Acceleration: the rate at which velocity changes. It is important to note that this change can be in speed, direction or both.

In the rotational motion we also have:

1-???Angular velocity: how fast an object rotates or revolves relative to another point.

2-???Centripetal acceleration: the rate of change in angular velocity.

More complex types of elements can be monitored in 3D objects and their movements. The best example for this could be the aircraft.?

Yaw:?The aircraft nose moves left or right around an axis that is running up and down.

?Pitch: The nose moves up or down about an axis running from wing to wing

?Roll: The rotation about an axis running from nose to tail.?

It is important to understand that our body does not feel velocity, but feels acceleration. A clear example is that more experienced drivers accelerate smoothly, whereas a learner driver produces a jerky ‘ride’ due to acceleration changes

The thrilling feeling, for the guest, is created through controlling and changing the acceleration for the ride cycle.

The following illustration shows the passenger coordinate system with orthogonal axes X, Y and Z (as shown in Figure 1). The Z- axes direction is defined along the spine (± 5° tolerance).

According to ASTM F 2137.?

The Biomechanical effect of Acceleration.

John Stapp of the US Air Force planned and conducted a series of tests on the effects of acceleration and deceleration, on himself. He travelled in a rocket powered sled at speeds greater than 65m/s. He is credited with proving that the human body can withstand elevated g- force, and survive at 46.2 g, although after the process he suffered headache, concussion, a fractured rib and wrist and a hemorrhaged retina.??

The acceleration time limit of G? and Gz is mentioned with the resulting symptoms in the Australian Standards for Amusement ride and design, AS 3533.1 Annex D Table D2.

The effects of a long duration of acceleration results in blood pooling and an increase in vascular pressure in the head and neck. Importantly, there are many factors that influence human tolerance to acceleration such as heat stress and hyperventilation, hypoxia, alcohol, hypoglycemia, inter-current infection, age, pregnancy and people with heart?disease. For these reasons it is with the upmost importance that we always have an instruction for use for each ride.

If we increase the exposure to a high acceleration, the changes to our overall health and physiological functionality would be detrimental. Our heart will work harder as it would be fighting against more gravity than it is used to in order to keep blood moving from our feet and our head to our heart. Breathing would also be more difficult as our diaphragm would have to work harder to change the volume of our thoracic cavity, allowing air to be pulled into and pushed out of our lungs.?

Newton’s second Law of Motion.

This law of motion exemplifies the relationship between force and acceleration on objects.

For a constant mass, force equals mass times acceleration, F = m.a.

The optimum thrilling feeling is created by the ride designers through generating acceleration in different directions, by applying different forces.

‘Jerks’ and ‘snaps’ are terms used by physicists to describe the passenger’s feeling inside the rides.

The difference between the purpose of the design behind amusement rides and transportation devices must be made clear. Engineers involved in the design of transportation devices try to minimize the feeling of acceleration whilst amusement ride engineers create changes in the acceleration, also staying within the limits that are specified in the standard to prevent the guest from suffering the consequences mentioned in part 3 of the article.

In order to verify if these specific standards are being followed, amusement ride engineers and inspectors use an accelerometer data logger to check the compliancy of the ride design in accordance with the code.

For the purpose of this article, three experiments on three different amusement rides were done to measure the acceleration and practice the interpretation of the data.?

Static Ride Position.?

What are the forces that act upon our bodies when we are on ride in a static position?

To simplify the case, let us imagine our body as a block on a platform which moves up and down when it is in operation, like an elevator.

In static position the forces affecting the block are as following:

The weight (W) of the body is the magnitude of the downward force it exerts on any objects which supports it. Thus, W = mg, where m is the mass of the body and g is the local acceleration due to gravity.

When the block is resting on the floor of the platform, the block experiences a downward force mg due to gravity. W in this example is the weight of the block. By definition, this is the size of the downward force exerted by the block on the floor of the platform. If we consider Newton’s third law of motion, the floor of the platform exerts an upward reaction force of magnitude W on the block.?

Ride In Operation.

Drop Tower

Drop and Twist is an Italian ride using a gondola suspended by a wire rope suspension system and lifted using a pneumatic cylinder which also controls the falling movement.?

The acceleration diagram of the ride is as follows;

The acceleration rate on Z is between 0.7 g and 1.5 g.?

In order to provide a lifting force for the gondola we will need a force greater than the weight force as following;

F1= Fg + Fnet hence the F1= m.g + m.ɑnet??→ F1= m (g + ɑnet)

Fg: equal to the weight force. ?Fnet : is the net force.

According to the graph, g + ɑnet = 1.5 g making the passengers feel heavier than normal when the gondola moves up. The net acceleration is +0.5 g as the ride moves in the positive direction, z.

When the gondola goes down, the force needed will be;

F2= Fg- Fnet hence the F2= m.g – m.ɑnet ??→ F2= m (g - ɑnet)?

According to the graph, g - ɑnet = 0.7g and that is how the passengers feel slight weightlessness when the ride drops. The net acceleration is negative, equal to -0.3 g, which provides deceleration towards the ground.

The small range of acceleration on X and Y is produced by the spinning movement in both directions.?

Zero Gravity.

Zero Gravity is an Italian ride consisting of a circular platform which revolves increasingly to a speed of 23 r.p.m. This speed causes friction between guests and the ride’s wall panel to become sufficiently large when the normal force from the wall increases with faster rotation. There is a hydraulic system that controls the platform and lowers it down when the panels rotate at 23 r.p.m giving the guest a flying feeling as their feet are not supported by the platform. The platform goes up again when the rotational speed is reduced.?

Velocity is a vector which consists of magnitude and direction.?

The changes in the velocity direction caused by a centripetal acceleration is given in the formula a = v2/r. This is how we can notice a high acceleration towards - X, which results in the guest being pushed against the panel.

To verify our measurement, we have manually counted the revaluation per minute which was 23 rpm converting this speed into linear speed considering 10m is the diameter of the platform.

R = 5 m.

N = 23 r.p.m.

V = 12 m/sec.

a = v2/r?

a = (8.9) 2/5 = 28.8 m2/sec = 2.8 g approximately equal to the result which was reached in our measurement.

The name Zero Gravity is not linked to the weightlessness feeling of the guest. Guests will continue feeling their weight. However, they will be pressed towards the wall with nearly three times their normal weight, due to the centrifugal force.?

Conclusion.?

It is undoubtedly clear from the information above that there are many aspects to consider when answering questions directed at the physics of entertainment rides and, importantly, the physical effects on the guests. It is with this information that we can understand, with some degree and insight, the challenges faced when designing and understanding the physics of rides. The rides designers and engineers, for these reasons, find it challenging to design the perfect amusement ride with complex motions in order to provide the maximum thrilling feeling without exceeding the biomechanical code limits. The complexities of physics and the challenges of ride design need to be acknowledged by new professionals, as they are fundamental in order to understand the workings and, importantly, the effects on the guests. This understanding and acknowledgement are essential not only for new professionals but for continued improvements and developments in this field of work.

Reference?

(1)??Beyond velocity and acceleration: Jerk, snap and high derivatives David Eager, Ann- Marie Pendrill and Nina Reistad.

(2)??BS EN 13814-1:2019 Safety of amusement rides and amusement devices. Design and manufacture.

(3)??AS 3533.1-2009 Amusement rides and devices- Design and construction.

(4)??Acceleration in one, two and three dimensions in launched roller coaster: Ann- Marie Pendrill.

(5)??Pendulum rides, rotation and the Coriolis effect: Ann- Marie Pendrill and Conny Modig.

(6)??Classical Mechanic by Richard Fitzpatrick, Associate professor of physics.?