View source for Wright State University Lake Campus/2018-1/Ping pong air drag

==From Wikipedia permalinks==
=====w:Reynolds number @ [[w:special:permalink/822809548]]=====
[[File:Vortex-street-animation.gif|thumb|right|A [[w:vortex street]] around a cylinder. This can occur around cylinders and spheres, for any fluid, cylinder size and fluid speed, provided that the flow has a Reynolds number between roughly 40 and 1000.]][[File:Air dry dynamic visocity on pressure temperature.svg|thumb|right|Pressure dependence of the dynamic viscosity of dry air at the temperatures of 300, 400 and 500&nbsp;kelvins]][[File:Drag coefficient on a sphere vs. Reynolds number - main trends.svg|thumb]]
The Reynolds number is defined as

:<math>\mathrm{Re} = \frac{\rho u L}{\mu} = \frac{u L}{\nu}</math>

where:
* <math>\rho</math> is the [[w:density]] of the fluid ([[w:SI units|SI units]]: kg/m<sup>3</sup>)
* <math>u</math> is the velocity of the fluid with respect to the object (m/s)
* <math>L</math> is a characteristic linear dimension (m).  [[w:special:permalink/822809548#Sphere_in_a_fluid|For a sphere L=2R is the diameter.]]
* <math>\mu</math> is the [[w:dynamic viscosity|dynamic viscosity]] (Pa·s or N·s/m<sup>2</sup> or kg/m·s)
* <math>\nu</math> is the [[w:kinematic viscosity|kinematic viscosity]] (m<sup>2</sup>/s).
=====w:Viscosity @ [[w:special:permalink/824605819#Air]]=====
The viscosity of air depends mostly on the temperature. At 15&nbsp;°C, the viscosity of air is 1.81x10<sup>−5</sup> kg/(m·s) 18.1&nbsp;μPa·s or 1.81x10<sup>−5</sup> Pa·s. The kinematic viscosity at 15&nbsp;°C is 1.4810x10<sup>−5</sup>m<sup>2</sup>/s or 14.8&nbsp;cSt. At 25&nbsp;°C, the viscosity is 18.6&nbsp;μPa·s and the kinematic viscosity 15.7&nbsp;cSt.

Here, 1 cSt = 1 mm<sup>2</sup>·s<sup>−1</sup> = 10<sup>−6</sup> m<sup>2</sup>·s<small>−1</small>.
=====w:Drag (physics) @ [[w:special:permalink/823381084]]=====
:<math>F_D\, =\, \tfrac12\, \rho\, v^2\, C_D\, A</math>

==Original effort circa 2/1/18==
From [https://wright000.miraheze.org/wiki/File:Pingpongairdragrolling.png this graph] we estimate an acceleration of 7 cm/s/s at a speed of 50 cm/s.

==2/8/18 Thursday phy2400 lab==
We will attempt to simulate this with Matlab:
* https://www.youtube.com/watch?v=cMUyv3d1uZo
* See also [https://met213.tech.purdue.edu/French/Example%20Problems/Ping%20Pong%20Ball%20Drop%20-%20Published%20Article.pdf met213.tech.purdue.edu ... Ping Pong Ball Drop]

I think we did the Reynold's number thing wrong.  I get Re=300 [http://airfoiltools.com/calculator/reynoldsnumber here], and that means C =1 [https://www.grc.nasa.gov/www/k-12/airplane/dragsphere.html here]

[[w:special:permalink/793658015|At sea level and at 15 °C air has a density of approximately 1.225 kg/m<sup>3</sup>]]

Ping pong ball: [[w:special:permalink/820593067|radius = 20mm; mass=2.7g]]