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The Chiropractic Impact Report

Courtesy of: Joseph Virga, D.C.

The Law of Inertia

Issac Newton

In world history, many consider the smartest person to ever have lived to be Sir Isaac Newton. Newton was an English physicist, mathematician, astronomer, natural philosopher, and theologian. Newton spent his career at the University of Cambridge. In 1687, at the age of 43, Newton published the book Principia Mathematic, which is among the most influential books in the history of science. 

In Principia Mathematic, Newton describes the three Laws of Motion. It is Newton’s Laws of Motion that explain contemporary whiplash trauma and subsequent injury. The most important Law is his first, often referred to as the Law of Inertia. Simply stated in the context of whiplash trauma, things at rest tend to remain at rest, and different parts of the same object can have different inertias. The larger the part and the more it weighs, the larger the inertia, or the greater its tendency to not want to move. 

The object in question in a whiplash trauma is a human body. The human body has two large parts that have their own separate inertia, the trunk and the head. These two large pieces of inertial mass (the head and the trunk) are connected by a thin pole, the neck. 

During a motor vehicle collision, a vehicle that is struck from behind will quickly move forward. As the vehicle moves forward, so do the passenger seats in the vehicle. As the passenger seat moves forward, so does the trunk of the passenger sitting in the seat. However, the head of the passenger in the seat does not move forward because the head has a separate inertia from the trunk. As the vehicle, the seat, and the trunk move forward from the collision, the head remains at rest, forcing the neck backwards.

The result is an inertial injury to the soft tissues of the vertebrae joints of the neck. Importantly, the neck does not hit anything; it sustains an inertial injury, similar to that seen in shaken baby syndrome.