# Kinetics (physics)

In physics and engineering, kinetics is the branch of classical mechanics that is concerned with the relationship between motion and its causes, specifically, forces and torques.[1][2][3] Since the mid-20th century, the term "dynamics" (or "analytical dynamics") has largely superseded "kinetics" in physics textbooks,[4] though the term is still used in engineering.

In plasma physics, kinetics refers to the study of continua in velocity space. This is usually in the context of non-thermal (non-Maxwellian) velocity distributions, or processes that perturb thermal distributions. These "kinetic plasmas" cannot be adequately described with fluid equations.

## Biomechanics and kinetics

One of the major components of kinetics is analyzing ones center of pressure. Center of pressure (COP) is often tested using a force plate in a biomechanics lab. Many scientists don't always have access to these expensive and unique equipment. Force plates can be any from thousands to tens of thousands of dollars. Scientist and students today have turned to an alternative way, by using Nintendo Wii Balance Board system as a force plate. One 2014 San Diego State University study has shown a correlation of ${\displaystyle r=0.99}$  for the center of pressure measured using the Balance Board compared to a gold standard measure.[5] The students expect their results to find that ankle bracing will reduce sway and decrease ankle instability and falls. Postural sway is the measurement of the time and distance a subject spends away from an ideal center of pressure. Measurement of a subject's center of pressure has been used as a method of quantifying postural stability. Investigators have theorized that if ankle injuries cause differentiation and functional instability, a subject's postural sway should be altered. Bracing has been known to provide cutaneous afferent feedback in maintaining postural control. The feedback follows the same neurological pathways in which the external ankle brace enhances the replication of the joint position.[6] Although some may argue that braces have a negative impact on sport performance, the effectiveness of their mechanical stability make them of high priority and necessity. Due to the high incidence of ankle injury, the control of stability and body sway remain of most importance in reduction of injury and better quality of life.

The term kinetics is also used to refer to chemical kinetics, particularly in chemical physics and physical chemistry.[7][8][9][10][11] In such uses, a qualifier is often used or implied, for example: "physical kinetics", "crystal growth kinetics", and so on.

## References

1. ^ kinetics. Encyclopædia Britannica Online
2. ^ Louis Adolphe Martin (1907). Text-book of Mechanics. Wiley. p. Section X, pp. 69ff.
3. ^ Kinetics must not be confused with kinematics, the study of motion without consideration of the physical circumstances causing it (see, e.g., Edmund Taylor Whittaker (1988). A Treatise on the Analytical Dynamics of Particles and Rigid Bodies (Reprint of the Fourth Edition of 1936 with a foreword by William McCrea ed.). Cambridge University Press. p. Chapter 1. ISBN 0-521-35883-3.), which is a separate branch of classical mechanics.
4. ^ See this discussion.
5. ^ Chang, Jasper O. MA, ATC; Levy, Susan S. PhD; Seay, Seth W. BSc; Goble, Daniel J. PhD (May 2014). "An Alternative to the Balance Error Scoring System: Using a Low-Cost Balance Board to Improve the Validity/Reliability of Sports-Related Concussion Balance Testing". Clinical Journal of Sport Medicine. 24 (3): 256–262. doi:10.1097/JSM.0000000000000016.
6. ^ Pintsaar, A; Brynhildsen, J; Tropp, H (1 June 1996). "Postural corrections after standardised perturbations of single limb stance: effect of training and orthotic devices in patients with ankle instability". British Journal of Sports Medicine. 30: 151–155. doi:10.1136/bjsm.30.2.151. PMC 1332381.
7. ^ Lifshitz, E. M.; Pitaevskii, L. P.; Sykes, J. B.; Franklin, R.N. (1981). Physical Kinetics. Butterworth-Heinemann. ISBN 0-7506-2635-6.
8. ^ Alexeev, Boris V.; Alexeev (2004). Generalized Boltzmann Physical Kinetics. Elsevier. ISBN 0-444-51582-8.
9. ^ Gorelik, G. E.; N. V. Pavlyukevish; V. V. Levdansky; V. G. Leitsina; G. I. Rudin (1995). Physical Kinetics and Transfer Processes in Phase Transitions. Begell House. ISBN 1-56700-044-4.
10. ^ Krainov, Vladimir P.; Kevin Hendzel (1992). Qualitative Methods in Physical Kinetics and Hydrodynamics. Springer. ISBN 0-88318-953-4.
11. ^ American Chemical Society, Division of Physical Chemistry (1976). Evolution of Kinetics: A Centennial Symposium of the Division of Physical Chemistry, American Chemical Society. American Chemical Society.