Sars-Cov-2 Kinematics and Physical Distance to Prevent Infection

Oswaldo Ortiz Vera

Academic Professional School of Hydraulic Engineering, National University of Cajamarca, Peru

Abstract: The SARS-CoV-2 virus, which causes COVID-19 disease, has a spherical shape between 100 and 200 nanometers (nm) in diameter and weighs more than 100 attograms (ag). It very compact molecular structure (composed of proteins, aminotraspheres, lactic dehydrogenase, procalcitonin) makes it very sensitive to terrestrial gravitational attraction, whose weight is increased by the high adherence of water from atmospheric humidity and other chemicals. The World Health Organization (WHO) recommends maintaining a minimum distance between people of 1 m, while other agencies such as the Centers for Disease Control in the United States recommend 2 m.  The objective of the present work was to determine the trajectory or displacement of SARS-CoV-2 and to estimate the maximum horizontal distance reached once it is released from the contaminating focus (nose, or mouth of the person) of the emitting entity towards the fluid field of the atmospheric air, as well as to estimate the sedimentation time, in order to formulate recommendations to avoid direct infection. For this purpose, a simplistic and, at the same time, conservative mathematical model was proposed, which ignores the size of the saliva drops, based on the theory of projectiles launched from above into the fluid field of the atmospheric air under normal conditions. The results show that the trajectory of the coronavirus is a two-dimensional semi-parabola of second degree with a concave descending branch downwards and apex in the focus of contamination (nose, mouth) of the emitting entity. It was estimated that the horizontal maximum ranges are between 0.90 and 1.80 m, depending on the initial speed, and that sedimentation times vary between 5 and 10 seconds. Therefore, it can be concluded that the minimum distance between people, to avoid direct contamination, is approximately 2 m.

Key words: coronavirus, sedimentation time, maximum horizontal range, contagion, atmospheric air viscosity