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

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## From Wikipedia permalinks[edit | edit source]

##### w:Reynolds number @ w:special:permalink/822809548[edit | edit source]

The Reynolds number is defined as

where:

- is the w:density of the fluid (SI units: kg/m
^{3}) - is the velocity of the fluid with respect to the object (m/s)
- is a characteristic linear dimension (m). For a sphere L=2R is the diameter.
- is the dynamic viscosity (Pa·s or N·s/m
^{2}or kg/m·s) - is the kinematic viscosity (m
^{2}/s).

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

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^{−5}m^{2}/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 mm^{2}·s^{−1} = 10^{−6} m^{2}·s−1.

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

## Original effort circa 2/1/18[edit | edit source]

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 | edit source]

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/m^{3}

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