## What is the viscosity of air at standard conditions?

The viscosity of air depends mostly on the temperature. At 15 °C, the viscosity of air is 1.81 × 10-5 kg/(m·s) , 18.1 μPa·s or 1.81 × 10-5 Pa·s . The kinematic viscosity of air at 15 °C is 1.48 × 10-5 m2 /s or 14.8 cSt. At 25 °C, the viscosity is 18.6 μPa·s and the kinematic viscosity 15.7 cSt.

**What are the international standard atmosphere units?**

In the ISA model, the standard sea level pressure/temperature is 29.92 in. (1,013.25 mb) and 59°F (15°C). As atmospheric pressure decreases with height, the temperature will decrease at a standard lapse rate.

### What is the international standard atmospheric lapse rate?

6.50 ºC/km

Environmental lapse rate As an average, the International Civil Aviation Organization (ICAO) defines an international standard atmosphere (ISA) with a temperature lapse rate of 6.50 ºC/km (3.56 °F or 1.98 °C/1,000 ft) from sea level to 11 km (36,090 ft or 6.8 mi).

**What is the international standard atmospheric density?**

1.225 kg/m3

ICAO Standard Atmosphere Airspeed indicators are calibrated on the assumption that they are operating at sea level in the International Standard Atmosphere where the air density is 1.225 kg/m3.

#### What is standard atmosphere table?

It is defined as having a temperature of 288.15 K (15 oC, 59 oF) at the sea level 0 km geo-potential height and 101325 Pa (1013.25 hPa, 1013.25 mbar, 760 mm Hg, 29.92 in Hg).

**Is Torr the same as mmHg?**

The key difference between torr and mmHg is that the value of one torr can be obtained by dividing 101325 from 760, whereas the value of one mmHg is given exactly as 133.3224. While 1 torr equals 0.999 mmHg, I mmHg equals 1.0000004 torr.

## What is the ISA tropopause temperature?

The temperature remains at a constant value of -56.5°C (216.65°K) from the tropopause up to 20,000 m (65,600 ft). This ISA model is used as a reference to compare real atmospheric conditions and the corresponding engine/aircraft performance.

**Why is 75 of the atmosphere’s mass found in the troposphere?**

Gravity, combined with the compressibility of air, causes the density of an atmosphere to fall off exponentially with height, such that Earth’s troposphere contains 80% of the mass and most of the water vapor in the atmosphere, and consequently most of the clouds and stormy weather.

### What is the coefficient of viscosity of air?

Using a modified form of Wagstaff’s apparatus for measuring the coefficient of viscosity of air by the method of interference fringes and using capillary tubes, the value of η23°c has been found to be (1834·38±0·35)×10−7 c.g.s. units.