Anglican Church Grammar School Physics Amusement Park Physics: Model Roller Coaster Design Name: Brendan Ta Subject: Physics Class: 11 PH3 Teacher: LWB Roller Coasters 1. Abstract / Hypothesis of a Good Roller Coaster The roller coaster is a balance between safety and sensation. A good roller coaster gives its riders thrill sensations that will make them want to ride it again and again. The ride should still be as safe as possible, even though passenger ride a coaster for the death defying thrill. The key to a successful coaster is to give passengers the sensation of speed and acceleration, which all depends on the speed control. A good roller coaster has hills, dips, loops, curves, straights, and braking systems that obey the laws of physics. The first experiment will show that mass does not affect the velocity. It will do this by altering the mass of a toy car down a track from a fixed height. This will show there is no relationship between the mass and velocity. The second experiment will show the minimum velocity required to make a loop. It will do this by altering the heights of a toy car along a track and measure the minimum velocity at the top of the loop. This will be done for altering radii of loops. It will prove there is a relationship between the minimum velocity and the radius of the loop. The third experiment will show the maximum velocity that can be reached on hump before the ride becomes unsafe. It will do this by altering the heights of a toy car along a track and measure the maximum velocity over the hump. This will be done for altering radii of humps. This will prove that there is a relationship between the maximum velocity and the radius of the hump. By applying these theorem plus others to a roller coaster design it will be possible to break down the critical points and determine if the design is exciting and safe. Brendan Ta 11.PH.3 2 Roller Coasters 2. Introduction / Physical Principles of Roller Coasters Energy exists mainly as: Kinetic energy, energy due to motion Potential energy, the energy that is stored A roller coaster works because of two things: gravity and the law of conservation of energy, i.e. energy can change from one form to another but cannot be neither created nor destroyed. A motor does the work to get you up the first hill and as you travel up the hill, the coaster stores more and more potential energy. That potential energy is converted into kinetic energy as gravity pulls it down the first hill. The further you go down the hill, the greater the velocity, and the more potential energy is changed into kinetic energy. The ride is fastest at the bottom of the hill because more and more potential energy has been converted into kinetic energy. In other words, the coaster trades height for velocity, or vice versa. As you go up the next hill, kinetic energy is changed into potential energy and the carriage slows down. The higher you go, the more energy is changed and you feel the car slow down. The total energy neither increases nor decreases; it just changes from one form to the other. However, some energy is lost due to friction. This may include wind resistance, the rolling of wheels, and heat or sound energy. The wheels reduce friction: it's easier to let something roll than to let it slide. Roller coaster designers are aware of this, and therefore make each successive hill lower than the previous one. Frictional losses can be calculated by determining the difference between the total energy at any two given points. E lost = ME1 – ME2 E lost = (mgh1 + ½ mv21) - (mgh2 + ½ mv22) For example, on the Cyclone, energy is lost travelling from the top of the first hill to the top of the first loop. E lost = ME1 – ME2 E lost = (mgh1 + ½ mv21) - (mgh2 + ½ mv22) = (3500×9.80×32 + ½×3500×1.272) - (3500×9.80×21.7 + ½×3500×132) = 1100423 – 1040060 = 6.0 × 104 Joules The energy lost to friction was 6.0 × 104 J, travelling from the top of the first hill to the top of the first loop. On the Tower of Terror, there is a significant amount of energy lost due to friction throughout the ride. E lost = ½ mv2 - mgh = ½×6.0×103×522 - 6.0×103×9.80×89 = 8112000 – 5059300 = 3.1 × 106 J Brendan Ta 11.PH.3 3 Roller Coasters A unit that is used to describe forces we feel is the g. One g is equal to the force of earth's gravity. Ironically, despite its name, gravity isn't a g-force, but g-forces are measured in terms of what you feel when you are sitting still in the earth's gravitational field. Engineers often use g's as a "force factor" unit. The force factor gives people a way of comparing what forces feel like. On roller coasters, the highest g-forces are felt just as the carriage enters a loop and also as it exits a loop, as these are where the greatest changes in velocity and direction are. The lowest g-forces are felt at the top of the loops, as this is where riders feel “weightless”. Just before entering a loop Forces felt on loops Brendan Ta 11.PH.3 4 Roller Coasters The physiological affect a roller coaster has on it riders must be calculated because if there is unsafe g-forces fatal injuries could occur. G-forces can affect the rider’s heart rate, stress blood vessels, injure necks and backs and cause black out or even red outs. Larger riders when accelerating in any direction push against the restrains of the coaster much more than a lighter rider. A riders withstanding to these g-forces can depend on their size, age, pervious injuries and medical disabilities, this may cause, bruising, breaking bones or even internal injuries. A roller coaster designer must decide on how the restrains will work and how they will pull or push against riders. If the restrains do not have some cushion the riders maybe injured quite a lot more if they were hard. Another consideration the roller coaster designer has to make is how tall a rider can be to be safely harnessed in a ride. Many rides have height restrictions because of this. Roller coaster harnesses often fit very tightly on the rider; this is because if the rider is thrown around in there seat injuries result. Aged riders must also be aware that the high g-forces because older people may have brittle bones or heart conditions. A rider with a weak back or neck may also be injured by the jerky turns that may occur on a roller coaster. Pregnant riders should also avoid high g-forces and jerky movements. These are very dangerous to women which are holding a baby because it does cause changes to a developing baby. When g-forces occur in high amounts or for long amounts of time the body is affected in many ways. Collins Concise Encyclopaedia of Astronautics (1968), pp 3-4, states: “A man in fact can withstand very high accelerations provided their duration is cut as their magnitude increases.” Humans can instantaneously sustain up to 500g in car accidents or falls on hard surfaces and 12g when diving from a springboard into water. However, for safety and legal reasons, roller coasters should not exceed 3g’s for more than a few seconds when entering a loop. There are several types of g-forces that are felt by humans. Life Support: G-Forces states: (http://nasaui.ited.uidaho.edu/nasaspark/safety/lifesupport/gforces.html) “The name of the G-Force is based on the direction of force with respect to the long axis of the body. The inertial force is the primary factor that produces physiological effects on the body during acceleration.” Brendan Ta 11.PH.3 5 Roller Coasters Positive g-forces occur when an accelerative force is applied from head to foot on the body, making the rider feel pushed down in the seat. As the blood pools away from the head, a condition called grey-out may occur. Negative g-forces occur when an accelerative force is applied from foot to head on the body, lifting the rider up out of the seat. The blood pools in the head, and with the increase pressure, vision turns red (redout), and the eyeballs feel like they are popping out. Transverse g-forces occur when the accelerative forces act across the body in a back to chest or chest to back direction. Lateral g-forces occur when accelerative forces act across the body in a side-toside direction. Several factors affect the strength of lateral G forces: the speed of the train, the tightness of the curve, and the amount of banking. As the g-forces climb toward 5g, you feel five times your weight and sink further into your seat. You can no longer see colour, only black and white. Next your field of vision begins to shrink and it feels like you are looking through a pipe. Your peripheral vision disappears as the visual pipe's diameter gets smaller and smaller. You feel heavier and heavier as the g-force increases. In a flash you see black. You have just experienced “blackout”. You remain unconscious until the g-force declines and the blood returns to your brain. Extended periods of blackout will lead to fainting, permanent brain damage, chronic seizures, heart failure, and death. This is avoided as much as possible by designers and insurance companies, and would limit repeat potential riders. Most roller coasters keep the g's felt under 5 g's on an inside loop or the bottom of a dip after a hill. When a rider travels over a hill very quickly, he experiences negative g's. A negative g is the multiple of a person's weight that is needed to keep a rider in his seat. Negative g's also force the coaster car to try to come up off the track. Tony Wayne states: (http://141.104.22.210/Anthology/Pav/Science/Physics/book/) “Negative g's are a rider's heaven and a designer's nightmare. Negative g's are avoided as much as possible.” A negative g however, has a different effect on a rider compared to a positive g. Both negative and positive g's can cause a rider to pass out. However, negative g’s cause a “redout”. A redout occurs when there is too much pressure on the brain caused by a surplus blood flowing into the head. The high pressure can cause blood vessels to burst and kill the rider. This is a sure way to limit the number of repeat riders. Brendan Ta 11.PH.3 6 Roller Coasters Weightlessness and heaviness are linked with the normal force; but have little to do with gravity. The normal force is smaller at the top of the loop and larger at the bottom of the loop. The normal force is large at the bottom of the loop because the normal force must be greater than the outward gravity force in order for the net force to be directed inward. At the top of the loop, the gravity force is directed inward and thus, there is no need for a large normal force in order to sustain the circular motion. The fact that a rider experiences a large force exerted by the seat upon her body when at the bottom of the loop is the explanation of why she feels heavy. In reality, she is not heavier; only experiencing the large magnitude of force which is normally exerted by seats upon heavy people while at rest. Gforces can be calculated by dividing the acceleration by 9.8ms -2, or by taking readings from the vertical and horizontal accelerometers, which in turn can be converted into accelerations by multiplying it by 9.8ms-2. However, when determining the g-force vertically, 1g must be subtracted from the final result to account for gravity, which is always present. Tower of Terror Horizontal accelerometer reading going up was 0.7g. aH = 0.7g Therefore, aH = 7ms-2 Just before the car enters the upward curve, the vertical accelerometer was 3.5g. acA = 3.5g Subtract 1g acA = 2.5g Therefore, aH = 24.5ms-2 T o w e r o f acA = 2.5g aH = 0.7g T e r r o r Brendan Ta 11.PH.3 7 Roller Coasters Cyclone At top of loop, g-force = ((v2/r)-g) ÷ g = ((12.52/8)-9.8) ÷ 9.8 = 1.0 At bottom of loop, g-force = ((v2/r)+g) ÷ g = ((20.62/7.9)+9.8) ÷ 9.8 = 6.5 Gravitron R Top = 5.6m 1m R = 5m 1m R Bottom = 4.4m 30° Χ = tan 30° Χ = 0.6m Therefore, R Top = 5.6m, R Bottom = 4.4m χ 1m 30° acA Top = 42r/T2 = (42 × 5.6) ÷ 2.6052 = 32.6ms-2 = 3.3g acA Bottom = 42r/T2 = (42 × 4.4) ÷ 2.6052 = 25.6ms-2 = 2.6g Brendan Ta 11.PH.3 8 Roller Coasters 3. Diagram of Roller Coaster Design Total length of rail: Mass of train: Passenger Capacity: Max speed: Lift-up mechanism: Ride time: Conveyor system: approx. 2200m 3000kg 20 persons 28ms-1 (100kmh-1) Conveyor chain approx. 4 minutes (includes loading and unloading) Lift-up speed: 2 ms-1 Angle of lift: 30° “The Spine Melter” Brendan Ta 11.PH.3 9 Roller Coasters 4. Analysis of Roller Coaster Design The “Spine Melter” has been designed to give riders a death-defying thrill sensation while at the same time being safe. It incorporates a steep first hill climb and fall, slopes, a helix, two vertical loops, and a banked curve. The train, with a mass of 3000kg, exits the station and is pulled up the first hill with height of 40m by a conveyor chain at a steady 2 ms -1. When it reaches the peak, the train’s centre of mass will have a velocity of zero. ME = mgh + ½ mv2 ME = (3000×9.8×40) + 0 ME = 1,176,000J v=0 v = 2ms-1 v = 28ms-1 40m As it travels down the incline, it reaches its maximum speed of 28ms -1 and enters the first slope (15m) with a velocity of 22.14ms-1 and the second slope (10m) at 24.25ms-1. 1st slope ME = mgh + ½ mv2 1,176,000 = (3000×9.8×15) + (0.5×3000× v2) 1500 v2 = 735000 v2 = 490 v = 22.14ms-1 2nd slope ME = mgh + ½ mv2 1,176,000 = (3000×9.8×10) + (0.5×3000× v2) 1500 v2 = 882000 v2 = 588 v = 24.25ms-1 Brendan Ta 11.PH.3 10 Roller Coasters At B, about 4% of energy to friction, leaving 1128960J left. The train then enters a helix with a radius of approx. 5m at about 20.48ms-1. ME = mgh + ½ mv2 1,128,960 = (3000×9.8×17) + (0.5×3000× v2) 1500 v2 = 629160 v2 = 419.44 v = 20.48ms-1 Using circular motion ac = v2/r ac = 20.482/5 ac = 84ms-2 It continues on a steady descend for about 200m at the same velocity. At C, about 10% of energy to friction, 1058400J left. It enters the first loop with at about 26.2ms-1 and at the top has a velocity of 17.7ms-1. The loop has a radius of 17m at the bottom, 10m at the top, and a height of 28m. ME = mgh + ½ mv2 1,058,400 = (3000×9.8×1) + (0.5×3000× v2) 1500 v2 = 1029000 v2 = 686 v = 26.2ms-1 G-forces At top of loop, g-force = ((v2/r)-g) ÷ g = ((17.72/10)-9.8) ÷ 9.8 = 2.2 At bottom of loop, g-force = ((v2/r)+g) ÷ g = ((26.22/17)+9.8) ÷ 9.8 = 5.12 At D, approx. 15% of energy has been lost to friction, 999600J left. The train enters the loop with a velocity of about 25.8ms-1 and at the top the velocity will be about 16ms-1. The loop has a radius of 14m at the bottom, 9m at the top, and a height of 26m. ME = mgh + ½ mv2 999,600 = 0 + (0.5×3000× v2) 1500 v2 = 999,600 v2 = 666.4 v = 25.8ms-1 Brendan Ta 11.PH.3 11 Roller Coasters G-forces At top of loop, g-force = ((v2/r)-g) ÷ g = ((162/9)-9.8) ÷ 9.8 = 1.9 At bottom of loop, g-force = ((v2/r)+g) ÷ g = ((25.82/14)+9.8) ÷ 9.8 = 5.9 After exiting the second loop, about 20% of the total energy has been lost due to friction, with 940800J left. It then travels over a 15 m slope at 18.25ms-1. ME = mgh + ½ mv2 940,800 = (3000×9.8×15) + (0.5×3000× v2) 1500 v2 = 499800 v2 = 333.2 v = 18.25ms-1 The train, with its velocity already greatly reduced due to friction, enters a banked curve tilted at 30° to the horizontal. R = (18.152×tan30)/9.8 R = 19.6m G-Forces g = 1/sin30 g=2 Brendan Ta 11.PH.3 12 Roller Coasters Finally, the brakes are applied to the train to bring it to a gradual halt. The total energy is 940800J, and the train must still travel 100m until it reaches the station. Braking force W = ∆E W = Fs 940,800J = 100F Therefore, F = 9408N The average braking force is 9408N Overall, 25% of the total mechanical energy was lost due to friction. 5. Conclusion The Spine Melter compared quite well with the Cyclone and Cyclone, which reached speeds of 23.6ms-1 and 24.2ms-1respectively. The Superman Krypton Coaster at Six Flags Fiesta, Texas, is a similar roller coaster to the Spine Melter. It can reach higher velocities (31.3ms-1), greater heights (51.2m), but its duration much shorter in length (2:35). It is arranged in 3 trains with 8 cars per train. Riders are arranged 4 across in a single row for a total of 32 riders per train. It also has a very high and steep first hill, and many inversions. It seems that the higher the first hill is and how far it drops, the greater the velocity reached by the train. However, most would feel the greatest thrills occur during the loops and in the dives. Riders feel sudden changes in velocity and direction, which have a lasting effect on them. It is important that roller coasters do not exceed 5g’s or low negative g-forces for any more than an instant. Coaster designers try to avoid these as much as possible, as extended redouts and blackouts can result in deaths, which will severely affect the number of repeat and potential riders, and also cause many legal battles. Above all, roller coasters should be a balance between safety and sensation. Superman Krypton Coaster at Six Flags Fiesta, Texas Brendan Ta 11.PH.3 Cyclone, Dreamworld 13 Roller Coasters Bibliography Collins Concise Encyclopaedia of Astronautics (1968), pp 3-4 http://www.esc20.net/etprojects/formats/webquests/spring2001/holmeshealth/Am usementParkPhysics/default.html http://141.104.22.210/Anthology/Pav/Science/Physics/book/ http://www.learner.org/exhibits/parkphysics/ http://nasaui.ited.uidaho.edu/nasaspark/safety/lifesupport/gforces.html http://www.thinkquest.org/library/lib/site_sum_outside.html?tname=C005075F&ur l=C005075F/English_Version/coasters.htm http://www.chebucto.ns.ca/~ak621/CEC/Co-Phys.html http://www.rcdb.com/installationdetail605.htm http://www.ed.uri.edu/smartprojects/rcoaster.html Brendan Ta 11.PH.3 14 Roller Coasters Experiment 1 Aim: To show that the mass does not affect the velocity of a roller coaster when released from a constant height. Introduction: Physics laws show that mass does not affect velocity. This means if a roller coaster carries a heavier load this will not affect how it runs the course aiming it safe no matter what the load. Mass does however corse more friction and this would mean small variation in results. This means that there is no relationship between mass and velocity. It is a common misconception of riders that if they have a heavier load their ride will change in speed. This experiment will disprove this misconception. The track and toy-car will be set up and released from a fixed height along with Data Studio using and picket fence and photogate to measure the velocity. Using this set up will show that there is no change except the slight changes from friction on the velocity when the mass is changed thus proving there is no relationship between mass and velocity. Procedure: 1. Height was chosen 2. Track and Data Studio using picket fence and photogate was configured 3. Toy car was released from fixed height along track. 4. The velocity was measured at the bottom of the track 5. This was repeated for each varying mass three times. 6. Results were put into an appropriate table. 7. Average was recorded. Car Incline 49cm Photogate Brendan Ta 11.PH.3 15 Roller Coasters Results: Mass of toy car= 37g height of release=49cm 1 2 3 4 Mass of toy-car and weights (g) 47 57 87 97 Velocity (ms-1) Velocity (ms-1) Velocity (ms-1) Average Velocity (ms-1) 1.39 1.39 1.41 1.41 1.39 1.39 1.39 1.39 1.39 1.39 1.39 1.41 1.39 1.39 1.40 1.40 The table shows the toy car’s velocity at the bottom of the ramp. The readings are very similar meaning they are both precise and accurate. The velocity changed very little proving there is no relationship between velocity and mass. Conclusion: This experiment proved that there is no relationship between mass and velocity at a fixed height. Discussion: This experiment demonstrated that there is no relationship between mass and velocity at a fixed height. The original theory that mass does not affect velocity is true. Many errors may have also affected the readings: Releasing of the car non-uniformly. Car moving out of rails. Friction. Improvements could be made to increase the accuracy of the experiment. Use of a better way of releasing the cars uniformly, perhaps a gate that can be lifted so the car is not pushed faster or dislodged from rails or starting point. Brendan Ta 11.PH.3 16 Roller Coasters Experiment 2 Aim: To prove the relationship between the minimum velocity and the radius of a loop. Introduction: Velocity is exponentially proportional to the radius of a loop. The velocity gained at the top of the loop must be high enough to maintain enough g-forces so that it can stay on the track, this is called the minimum velocity. The theory states V 2min = (Rg) thus meaning the minimum velocity needed is exponentially related to the radius of the loop. If the cart does not maintain this minimum velocity at any part along the loop it will fall off or stop. Roller coasters rely on big turns and high g-forces to excite riders. It is common for riders to think that not matter how fast they are going they will always make a loop. Physics theory however states that a minimum velocity must be reached for the ride to make the entire loop. When a roller coaster is being designed, designers must used physics to find if the ride has enough speed and energy to make a loop. If this speed is too slow the coaster may stop or even fall off. The experiment will display the relationship between the minimum velocity and the radius by realising the toy car at varying heights to find the minimum velocity required to make the loop. This will be done with differing radii. This will then prove the exponential relationship between minimum velocity and radius of a loop. By knowing this it can then be applied to our roller coaster design. This experiment will prove the relationship between the velocities required to complete loops of differing radii. A car and track formed into a loop will be used along with Data Studio to find the velocity. Procedure. 1. Track and photogate and picket fence were calibrated. 2. Data Studio configured. 3. Four differing radii were chosen. 4. Toy car was released at differing heights on the track. 5. Minimum velocity was recoded at the top of the loop. 6. Repeated 3 times for each loop of differing radii. 7. Results put into table. 8. Average of results calculated and recorded Brendan Ta 11.PH.3 17 Roller Coasters Car Start ramp Photogate Loop Results: 1 2 3 4 Radius (m) Velocity 1 (ms-1) Velocity 2 (ms-1) Velocity 3 (ms-1) 0.070 0.105 0.160 0.190 0.870 1.06 1.28 1.32 0.810 1.04 1.30 1.39 0.880 1.07 1.30 1.42 Average Velocity (ms-1) 0.850 1.06 1.29 1.37 The table shows the velocity of the car at the top of the loop of differing radii. The table shows the velocities were very similar meaning that they were both accurate and precise. As the radius increased so did the velocity adhering to our theory of exponential relationship. Sample Calculations. V2= (Rg) V= √ (Rg) V= √ (0.105 x 9.80) V= 1.01 ms-1 (Experiment result was 1,06 thus meaning a 5% of error) Conclusion: This experiment proved the exponential relationship between minimum velocity that the car needed to go around the radius of the loop. Brendan Ta 11.PH.3 18 Roller Coasters Discussion: This experiment demonstrated that when the radius of the loop is made bigger the minimum velocity needed to complete the loop increase. The theory that the minimum velocity is exponential to the radius is a correct theory. Many errors may have also affected the readings: Releasing of the car non-uniformly. Car moving out of rails. Improvements could be made to increase the accuracy of the experiment. Use of a better way of releasing the cars uniformly, perhaps a gate that can be lifted so the car is not pushed faster or dislodged from rails or starting point. Brendan Ta 11.PH.3 19 Roller Coasters Experiment 1 Aim: To find the relationship between the maximum velocity and radius of a hump. Introduction: The maximum velocity is exponentially related to the radius of a hump. The velocity at the top of the hump must be lower than the maximum velocity. Physics theory statesV2= (Rg) where the maximum velocity is exponentially proportional to the radius of the hump. If this velocity is to high the object may be come derailed or even air-born meaning the ride would be very dangerous. Most riders assume that no matter what velocity they are travelling at they will always make the hump safely. As according to physics theory there is a limit to this velocity and this experiment will prove this theory. Designers of roller coasters must find this maximum velocity and must not come close to it or exceed it or the ride becomes very dangerous. This experiment will show this exponential relationship between the maximum velocity and the radius of the loop. It will do this using a toy car and track set up with a hump along with Data Studio to measure the velocity at the top of the hump. This experiment will use the toy car and hump at varying heights to find the maximum velocity over the hump and also varying radii. The maximum velocity will be measured using a picket fence and photogate set up. Using this procedure the exponential relationship between the maximum velocity and radius of the hump can be proved. Procedure: 1. Track and photo gate and picket fence calibrated. 2. Data Studio configured 3. Four differing radii were chosen for the humps. 4. Toy car released from carrying heights on the track. 5. Maximum velocity was measured at the top of the hump 6. Repeated three times for each different hump. 7. Results put into table 8. Average taken and results graphed in excel. Brendan Ta 11.PH.3 20 Roller Coasters Car Results: Starting ramp Photogate Hump 1 2 3 4 Radius (m) Velocity (ms-1) Velocity (ms-1) Velocity (ms-1) 0.045 0.060 0.090 0.115 0.65 0.73 0.97 1.09 0.61 0.75 0.99 1.07 0.63 0.75 0.99 1.12 Average Velocity (ms-1) 0.63 0.74 0.98 1.09 The table shows that the readings were very similar meaning they were both precise and accurate. It shows that as the radius of the hump raised so did the maximum velocity signifying at exponential proportionality. Sample Calculations: V2=(Rg) V= √ (Rg) V= √ (0.045 x 9.80) V= 0.66 ms-1 (Experiment result was 0.63 giving a 5% error) Conclusion: The experiment proved the theory that maximum velocity is exponentially proportional to the radius of a hump. Therefore it can be said that velocity is close to directly proportional to the radius of the hump. Brendan Ta 11.PH.3 21 Roller Coasters Discussion: This experiment demonstrated that when the radius of the hump is made bigger the maximum velocity that is required to stay on the track increased. The theory that the maximum velocity is exponential to the radius is a correct theory. Many errors may have also affected the readings: Releasing of the car non-uniformly. Car moving out of rails. Improvements could be made to increase the accuracy of the experiment. Use of a better way of releasing the cars uniformly, perhaps a gate that can be lifted so the car is not pushed faster or dislodged from rails or starting point. Brendan Ta 11.PH.3 22