Vertical Velocity - roller coaster - was created in 2001.
Velocity is constant when the middle of the roller coaster is parallel with the ground (when the tangent of the curve the roller coaster is on has a slope of 0 at the center of mass of the roller coaster).
Twister - roller coaster - was created in 1999.
Sleeping on a Roller Coaster was created in 1992.
Tremors - roller coaster - was created in 1999.
Stealth - roller coaster - was created in 2006.
Rattler - roller coaster - was created in 1992.
Hades - roller coaster - was created in 2005.
Whirlwind - roller coaster - was created in 1993.
Thunderbird - roller coaster - was created in 2006.
Demon - roller coaster - was created in 1976.
Whizzer - roller coaster - was created in 1976.
Balder - roller coaster - was created in 2003.