According to Douglas Smith and David Meaney, professors at the University of Pennsylvania, roller coasters do not produce enough gravitational force (g-force) to cause swelling or bleeding of the brain (Smith, 2002). Gravitational forces are forces that act on the body due to acceleration or gravity. The study authors state that, even in the worst-case scenario, the head rotational accelerations experienced by roller coasters are never strong enough to cause serious brain damage (Smith, 2002). Professor Smith and Meaney conducted their studies using many roller coaster rides such as the Rock 'n' Roller Coaster at the Disney-MGM studio park in Florida, Speed-The Ride at the Nascar Café in Las Vegas, Nevada, and Face- Off to Kings Island in Ohio (Smith, 2002). However, after reading the article I noticed some flaws in their study. For example, they didn't use extremely fast roller coasters like Kingda Ka, which can reach speeds of up to 128 miles per hour. They also only studied extremely healthy people. They did not study children or adults with previous health problems. According to Robert Braksiek there are several roller coasters that are capable of causing enough G forces to stimulate subdural hematomas (when blood collects between the Durameter and the brain) in passengers on these roller coasters (Braksiek, 2002). With sufficient shear forces it can be severe enough to rupture the cortical veins leading to a subdural hematoma (Braksiek,