G-FORCES
So far we've talked about energy, but there's another way to explain the change in speed.
Why don't you need a chain to drag the coaster down the first slope? The answer is, gravity. The front car of the coaster has weight. Its weight gravity pulls it down the slope. Since the cars on a coaster are connected, the first car pulls the others along. Each time a car passes the edge, its weight adds to the total pull down the slope.The coaster starts down the slope slowly, but as time increases, the coaster moves faster and faster. The change in the rate of speed is called acceleration.. During the descent, speed increases. You go faster and faster until you hit bottom. At that point you're still moving very fast, but the speed is less scary. Gravity no longer pulls the coaster along the track.
Gravity comes into play again on the next hill, but this time, gravity pulls backward on the coaster. As the coaster climbs to the top of the second hill, it moves slower and slower. If the hill is short, the coaster may still be moving fast when it reaches the top of the hill. If the hill is high, the coaster could slow to a crawl. Since that wouldn't be much fun, the hills are kept short. That way, you always move fast, even at the top of a hill.
Galileo Galilei studied objects in free fall and determined that an object will fall downwards with a constant acceleration due to gravity. The lower case letter 'g' is used to represent the earth's gravitational constant and the established value of g used for calculations is 9.8 meters/sec./sec. or 32.15 ft./sec./sec.
Speed, however, doesn't travel unaccompanied; also generated are G's. These, it's important to point out, are not the same things as "Gees," which are often produced by people who are actually having fun. G's are forces we experience due to very great changes in speed ( accelerations). Take a look at this good loking dude ( Ms. Starkey's boyfriend) as he pulls close to 8 G's on a rocket sled .
When a roller coaster car is stationary on flat track the riders weight is pressing downwards on the seat with a force equal to their mass multiplied by the earth's gravitational acceleration 'g'. We can say they are experiencing a force of '1G' due to their normal weight.
G forces are part of the thrill of the ride. As you speed through the curve at the bottom of hills or at the base of a loop you pull positive G's. You actually feel heavier as these forces push you into your seat. At the bottom of loops it is not uncommon to pull 4 G's, 4 times your weight. this about the limit of comfort for most people. At 6 g's nosebleeds occur, at 8 G's they will brown out, at 10 g's, blackout, and at 14 G's....DEATH.
Positive G-forces accumulate only when the coaster is climbing. As it speeds downhill, the pull of gravity is actually reduced, producing "negative g's," or a feeling of weightlessness. Astronauts orbiting the Earth experience zero-g. On a roller coaster we go no lower than .2 g. This is enough to give people the thrill of being airborne but, in a worst-case scenario, keeps them in the car if the lap bars or seat belts fail.
When freely accelerating down a slope, you feel pleasantly lighter
50% lighter on the 60° drop slope of the Magnum at Cedar Point in Sandusky,
Ohio. There is no forward or backward pull. Big people, little kids, and
the roller-coaster train all accelerate the same way.
Riders accelerate down the 60° slope of the first hill of the Magnum at 4.9 m/s2 (16 ft/s2), weighing about one-half of their normal weight, and anticipating a journey through the valley at 121 km/h (75 mph) where they will feel as much as 3.5 times their normal weight and experience a blurring of vision as their blood slowly leaves their brains.
Designers rely on the acceleration caused by those forces to make a roller coasterride both thrilling and safe. The trick is knowing how to use the forces properly. If the forces are too great in one direction, for instance, they'll throw the car off the track. If an upward force is too large (giving you a feeling of heaviness), your heart cannot pump enough blood to your head and you faint. On the other hand, the lack of supporting forces can create feelings of incredible lightness. This can provide an electrifying ride that delivers you safely to the end.