J Manipulative Physiol Ther. 1990 May; 13(4): 204-6.

The physics of spinal manipulation. Part I. The myth of F = ma.

Haas M.

Research Department, Western States Chiropractic College, Portland, Oregon 97230.

The product of the adjusting physician's mass and acceleration does not quantify the adjustive force as popularly believed, an error stemming from a misunderstanding of Newton's second law. In this paper, a gedanken experiment illustrates the misapplication of F = ma and suggests that the adjustive force depends on the impact velocity, mass of the doctor, and intrinsic physical properties of the doctor and patient.