Thrills without spills.
Abandon all hope," warns the sign above the spinning rotor ride at the Coney Island amusement park in New York City. But that didn't stop Lourdes Gonzalez, 24, and dozens of other thrill seekers from climbing aboard last July.
At first, everything ran as scary - but as "normal" - as usual, Gonzalez says. She and the other passengers lined up along the inner rim of the barrel-like ride. The operator set the barrel spinning and the liders were "glued" to the wall. When the floor dropped out, they felt like they were flying.
But suddenly - Kablam! - the passengers really were flying - out of the ride. The accident mangled Gonzalez's right leg; 12 other people suffered back injuries and bruises.
What went wrong? Inspectors found that a huge metal strap, which held the barrel's wall panels together, suddenly snapped in two. "One of the panels struck the operator's booth and that portion of the barrel tore open," says Vahe Tiryakian, spokesperson for the New York City Department of Buildings, which inspects amusement-park rides. Without warning, the passengers were flung through the gaping hole (see diagram, left).
That incident got me thinking: Just how safe are amusement-park rides? Could a speeding roller coaster go flying off the tracks? Could an accident like the rotor disaster happen again?
The answers depend largely on physics, says Ron Toomer, a mechanical engineer who designs roller coasters. Take the rotor incident. Normally, Toomer explains, the laws of physics keep the riders safely stuck to the rotor wall. Here's how:
When the barrel and floor start to spin, the people move too. At any given instant, the riders are moving sideways. And like all moving objects, they would keep moving in a straight line (sideways) if no other forces acted on them, Toomer says. That tendency to keep moving in one direction is called inertia. (Remember Newton's first law of motion? See SW 9/1/95, p. 12.)
But rotor riders can't keep moving in a straight line because the curved walls of the rotor get in the way. The riders "fly" into the wall and stay pinned - even when the floor drops.
For years, people thought an outward-pushing force, which they called centrifugal force, was what kept rotor riders pinned to the wall. But believe it or not, Toomer says, centrifugal force doesn't exist. What's really happening, he explains, is that inertia makes the riders fly outward. They feel pressed to the wall by the force of the wall holding them in. The center-pushing force that holds them in is known as centripetal force.
At Coney Island, when "the rotor wall panel suddenly "disappeared," Toomer explains, the centripetal force disappeared too. With no force to hold the passengers in, they flew off the ride.
The Coney Island rotor accident was probably the result of human oversight, Toomer says. (For example, someone may have missed a crack in the metal strap). But for most ride designers and inspectors, he says, "safety is the number-one priority."
Look at a giant roller-coaster loop, for example. It's similar to a rotor turned on its side, says Toomer. On the loop, the "pushed-to-the-wall," feeling created by centripetal force helps keep people in their seats - even when the coaster cars turn upside down.
Decades ago early roller-coaster designers tried to make perfectly circular loops. But they soon rejected that idea when they realized that gravity (Earth's downward pull) would slow the cars too much at the top of the loop. At such slow speeds, centripetal force would weaken to the point that gravity could pull riders to the round. Conversely, at the bottom of a circular loop, the riders would be moving so quickly that centripetal force would increase and squish the riders in their seats uncomfortably.
So instead, designers make teardrop-shaped roller-coaster loops (see photo.) This design tightens the curve at the top where the coaster train slows down. The tighter curve increases centripetal force, the force that keeps you pinned to your seat, Toomer says - so you don't fall out. At the bottom of the loop, where the train speeds up, centripetal force increases more. But because the curve is more stretched out, Toomer explains, you don't feel too squished.
Many other innovations keep rides scary - but safe. These include wheels embedded inside tubular steel tracks (to help keep ride cars - and riders - on track), and cushioned, over-the-shoulder harnesses (to keep you buckled in).
Designers also run the rides through dozens of trials before you ever climb on board. "It's always easy to find people who want to be the first to test a new coaster," Toomer says.
And inspectors routinely examine ride machinery, in some cases using X-rays to check metal rides for cracks or other problems that you can't see on the surface. Because of the Coney Island rotor accident, New York inspectors may soon require those tests.
Still, with all these safety measures, accidents do happen. In 1994, an estimated 7,200 people were treated in hospital emergency rooms for minor injuries (mainly bumps and bruises) associated with amusement-park rides, according to the U.S. Consumer Product Safety Commission. Though that number may seem high, says John Graff, executive director of the International Association of Amusement Parks and Attractions, you have to consider that 400 to 500 million people take billions of rides each year. "Most of the accidents occur because people are standing up, horsing around, or goofing off," he says.
Kind of makes you wonder: Maybe riding too many amusement-park rides can scramble your brains.
The challenge: Design the "Fling & Float," a ride that combines the thrill of amusement-park rides,
The setup: Riders sit in rafts attached to cords. A machine spins the rafts around a platform. At a certain point, each cord snaps and fling the rafting rider into a lagoon (see top-view diagram, below).
The catch: At what point on the spinner (A-D) should the cords detach so that riders land in the lagoon? This experiment may help you decide:
WHAT YOU NEED: rubber ball * 1-m (3-ft.) piece of string * partner * masking tape
WHAT TO DO:
1. Tie string securely around ball.
2. In an open area, hold the end of the string and swing the ball over your head, lasso style.
3. Predict: Where will the ball fall if you release the string when your arm is directly in front of you? Have a friend record your prediction.
4. Stop swinging and release the string simultaneously. (Make sure classmates are standing clear.) Was your prediction correct? With a piece of tape, record where the ball falls.
5. Repeat Steps 2 through 4 three times. Then try different release positions. Notice any patterns?
At what point on the "Fling" ride should you release each ride?
DON'T STOP NOW!
How does centripetal force help make your ride a success? What safety measures would you add?
RIDE WRECK: Disaster struck the spinning rotor ride at Coney Island, New York, last summer when passengers were flung from the ride. Here's what happened:
1 Riders entered the rotor through a door. 2 The operator closed the door and started the ride. 3 As the barrel spun at 97kph (60mph), riders felt pressed against the wall by centripetal force, the force holding them in. When the floor dropped 3m (10ft), riders felt like they were flying. 4 Suddenly, a metal strap holding the barrel together snapped. Part of the wall tore off. Without the inward push of centripetal force, riders flew off the ride - flung by their own inertia. Thirteen people were injured.
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|Title Annotation:||amusement park rides, the laws of physics, and safety|
|Date:||Nov 3, 1995|
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