Title: Jack Rabbit (Kennywood)
Content:  the ride was a tunnel which covered the turnaround section after the first drop, but this was removed in 1947 when the new cars were ordered. In 1991, the tunnel was restored, at a slightly shorter length. The Jack Rabbit was built shortly after Miller patented a new track design in 1920 (which all wooden coasters built since have used). This design involved the use of wheels both under and over the track, which allowed Miller to create the then enormous 70 ft drop that is the attraction's largest. It is most well known for its double dip element following the lift hill. The double dip produces strong airtime that makes the 
Title: Jaws (ride)
Content:  evacuated almost daily. Following the Summer opening of the park, Universal temporarily shut down the ride in August 1990 and sued Ride & Show Engineering, Inc. for failing to properly design the ride. Throughout 1991 and early 1992, Universal attempted to refurbish the effects of the ride for an eventual re-opening, but with no success. Some reports leaked that the high-tech electronics used in the sharks were damaged due to inadequate waterproofing. Eventually, Universal collaborated with Totally Fun Company, ITEC Entertainment, Intamin and Oceaneering International, who together installed an entirely new ride system and special effects to create an almost entirely new version 
Title: Jet Rescue
Content:  Riders board one of two trains, each featuring 16 jet skis. After being cleared to dispatch, the ride uses a hydraulic friction wheel mechanism to launch riders out of the station at a speed of 65 km/h. The ride then enters a wide, highly banked helix to the right before perpendicularly crossing over the launch track at a height of 6 m. The ride then dips to the left and an on-ride photo is taken. The track then levels out and enters a tunnel parallel with the station. Upon entering the tunnel, another set of friction wheels are activated to launch the riders to the faster 
Title: Jet Rescue
Content:  of 70 km/h. The opposite end of the tunnel is covered in mist preventing riders from seeing the approaching track. The instant that the train emerges from the tunnel it banks sharply to the right. This is followed by four quick, directional changing turns between rocks and past an animatronic sea lion. The track then elevates off the ground level to cross over the track a second time before entering the brake runs. The ride slowly makes its way into the unload station where riders disembark their jet skis and exit via the merchandise shop. On-ride photos and Jet Rescue merchandise can be purchased here.
Title: The Joker (S&amp;S Worldwide)
Content:  Riders on The Joker begin by climbing along a 120-foot vertical rise. Then zoom over hills while pivoting forward multiple times, before plummeting into a steep raven drop. Next, riders subsequently change directions and get to enjoy a backwards flip, spinning backwards into another raven drop and then ending with a forward flip. The roller coaster uses an adjustable series of magnetic kickers to allow the cars to spin freely, based on factors such as gravity and rider weight in the cars. The park can adjust the degree of spin based on rider input, which will help them regulate the experience to average rider tolerance over 
Title: Jaws (ride)
Content:  cable attached to a high-voltage barge). Oceaneering provided the animatronic shark for the redesigned ride, their first theme park-based project. The ride was then officially re-opened by Roy Scheider, Lorraine Gary and Steven Spielberg in Spring of 1993. On March 31, 2001, Jaws officially opened at Universal Studios Japan. The ride system for the attraction was developed by MTS Systems Corporation. Following the hurricanes that struck Central Florida in 2004, Universal was forced to temporarily close the ride in January 2005 due to the rising cost of petroleum, which was used to fuel the numerous pyrotechnical effects throughout the attraction as well as 
Title: Krampus Expédition
Content:  Numerous design changes were made to the Mack Rides water coaster hardware for Krampus Expédition, chiefly the usage of a new tri-tube track on the coaster portion. Past water coasters didn't use such, but updated standards led to a reinforcement of the track design. A mid-course brake run was also planned to be installed just before the final drop, but Rodolphe Gélis - critical of the concept - convinced engineers at Mack Rides not to do so by proving that it would have no effect on the ride's hourly throughput.
Title: Indiana Jones Adventure
Content:  Kingdom (opened as CTX: Countdown to Extinction). However, the Japanese counterpart uses linear-inductive actuators instead of three hydraulic rams. The 35 gallons of hydraulic fluid used on the Disneyland version takes two hours to clean up the track when a hose splits, in which if there is hydraulic failure, the vehicle is incapable of driving. Because of Japan's environmental codes regarding oil spills, the design team elected to substitute electromagnetic actuators on the ride vehicle. Three of these actuators are used to create a three-dimensional (pitch, roll, and elevation) motion platform chassis on which the car body sits. Heavy or light traffic 
Title: The Joker's Jinx
Content:  Joker's Jinx is located in the Gotham City section of the park near Superman: Ride of Steel roller coaster and Whistlestop Park. After boarding Joker's Jinx, riders are launched through a narrow launch tunnel into a "spaghetti bowl" of track which contains a cobra roll, a sidewinder, and many twists and turns. The coaster doesn't have a mid-course brake run like the similar rides at Kings Island and Kings Dominion; instead the coaster has multiple rings that the train goes through. After the rings, riders spiral downward and to the left, and after more twists and turns they pass through a corkscrew before arriving at the ride's final brake 
Title: Jaws (James Bond)
Content:  prodigious height but in temperament he followed his father and was surly and uncooperative, given to sudden outbreaks of violent temper. Because of his size he commanded a place in the university basketball team, but he was sluggish of reaction and his lack of speed was constantly exposed by more skilful but less physically endowed players. After a failed attempt at a basketball career, Krycsiwiki was arrested by the secret police for having taken part in the (fictitious) "1972 bread riots". While he was imprisoned, the police "beat him with hollow steel clubs encased in thick leather" until they thought he was dead, leaving his 

Question: what is the purpose of a jake brake?
Answer: slowing the vehicle.