FRYEBURG – Though visitors to the Fryeburg Fair might not be aware of it, the midway rides give them a bit of fun through physics.

“Most fair rides involve either lifting you up in the air and dropping you, which involves gravity, or changing your direction rapidly, which involves inertia,” said Karl Otterson, who has taught physics at Oxford Hills Comprehensive High School for six years.

Many of the rides at the fair involve rapid rotation.

The Orbiter spins a set of arms, each holding a trio of seats which spin in circles of their own.

As the rides speed up, the arms extend so the seats are spinning nearly perpendicular to the ground.

Part of the vertical rotation includes fighting against gravity at the bottom of the circle and getting assistance from gravity at the top, leading to alternating sensations of being crushed and being lightened.

Katherine Blauvelt, 10, of Farmington, said she wasn’t sure she would return to the ride.

“Maybe when I’m older,” she said. “Or maybe later.”

Jakob Bubier, 13, of Greene, had a more positive review. He said he enjoyed the dizziness the ride caused.

“It makes you feel like you’re sick, but not really,” Bubier said.

Rides that involve a smaller spinning circle within a larger one are fairly complex, Otterson said. The smaller the circle, the faster the speed needed to pull a person toward the center of the object. When both are in effect, the velocities are combined.

“That’s going to be the most extreme acceleration,” Otterson said.

He said centripetal force, which pushes toward the center of the rotation, is in play with the spinning rides. In the Gravitron, a saucer-shaped ride in which patrons are stuck to the wall, the side of the ride pushes inward against the back of a rider. In the YoYo, a set of swings rotated from a large turntable, the force is exerted on the seat of your pants.

Otterson’s favorite fair attraction, the bumper cars, are a little easier to explain.

“Essentially, the bumper cars are an inertia ride,” he said.

An object in motion will stay in motion in a particular direction at a constant speed unless acted upon by other forces, including gravity and friction. When the car bumps another one, you get jolted because your body keeps moving forward until the safety restraint kicks in.

The Zipper was easily identifiable from the screams of its riders. A long arm spins vertically on a central axis, and cages that spin freely are pulled around the arm like a conveyor belt.

“It was pretty scary,” said Adam Brulott, 16, of Limerick.

Otterson said The Zipper’s cages farther from the center make larger circles in the same amount of time. So, they move faster than the arm. With the addition of gravity, the motion can become intense when a cage reaches the end of the arm at the bottom of the ride.

“That’s easily the most complicated ride at the fair, I think,” Otterson said.

Many visitors were just getting started on the rides Thursday afternoon, and reactions were mixed. Fred Wheeler of Bethlehem, N.H., and Melody Sawyer, of North Conway, N.H., gave the Thunderbolt a try. This ride speeds people on a hilly, circular track in freely rocking carriages, then slows and goes in reverse.

“I hate rides, so they’re much better when I take Dramamine,” Wheeler said. “What we won’t do for women.”

“He did it to impress me,” Sawyer said.

Clayton Urquhart, 7, of Standish started his tour of the rides on the YoYo before heading to the bumper cars.

When asked how many rides he planned to go on, Urquhart replied, “A hundred!”