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

From Wikiversity
Jump to navigation Jump to search

From Wikipedia permalinks[edit]

w:Reynolds number @ w:special:permalink/822809548[edit]
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.
Pressure dependence of the dynamic viscosity of dry air at the temperatures of 300, 400 and 500 kelvins
Drag coefficient on a sphere vs. Reynolds number - main trends.svg

The Reynolds number is defined as

where:

w:Viscosity @ w:special:permalink/824605819#Air[edit]

The viscosity of air depends mostly on the temperature. At 15 °C, the viscosity of air is 1.81x10−5 kg/(m·s) 18.1 μPa·s or 1.81x10−5 Pa·s. The kinematic viscosity at 15 °C is 1.4810x10−5m2/s or 14.8 cSt. At 25 °C, the viscosity is 18.6 μPa·s and the kinematic viscosity 15.7 cSt.

Here, 1 cSt = 1 mm2·s−1 = 10−6 m2·s−1.

w:Drag (physics) @ w:special:permalink/823381084[edit]

Original effort circa 2/1/18[edit]

From this graph we estimate an acceleration of 7 cm/s/s at a speed of 50 cm/s.

2/8/18 Thursday phy2400 lab[edit]

We will attempt to simulate this with Matlab:

I think we did the Reynold's number thing wrong. I get Re=300 here, and that means C =1 here

At sea level and at 15 °C air has a density of approximately 1.225 kg/m3

Ping pong ball: radius = 20mm; mass=2.7g