8.1 Physics of the Atmosphere Flashcards
What is the SI system?
Based on the metric system and must be used as law throughout the world
What are the four fundamental units in aerodynamics?
Mass
Length
Time
Temperature
What is the unit of measurement for mass and how is it denoted?
Kilograms (Kg)
What is 1Kg measured against?
1 kilogram is also the volume of one litre of pure water at a temperature of 4° Celsius
What is constant for astronauts in space; Weight or Mass?
Mass as weight is varied by gravity
What is the unit of measurement for Length and how is it denoted?
Meteres (m)
What year was the metre introduced and by whom?
French Government, 1790
How is a metre defined?
A certain number of wavelengths of a particular colour of light.
What is the unit of measurement for Time and how is it denoted?
Seconds (s)
How is a second defined?
A fraction of the unchangeable speed of light.
What is the unit of measurement for Temperature and how is it denoted?
Kelvin (K)
What are the 6 basic quantities?
Speed Acceleration Power Pressure Force Work
What is the unit of measurement for Speed and how is it denoted?
Velocity (v)
How do you calculate acceleration?
Time
What is the unit of measurement for Acceleration and how is it denoted?
a (M/s*2)
What is the unit of measurement for Acceleration due to Gravity and how is it denoted?
G (9.8m/s*2)
What happens to persons weight if they are moving in an elevator with a constant velocity?
No change in weight
What happens to persons weight if they are moving in an elevator which accelerates when moving up?
As the elevator accelerates, there is an additional force which increases the weight
What is Newtons second law?
F=ma
How do you calculate weight, and what is its’s units?
W=mg
Unit - Newtons
How do you calculate work done, and what is its’s units?
Work = N x m
Work is denoted by Joule (J) and is measured in Newton metres
How do you calculate Power, and what is its’s units?
Power = Force x Distance/ Time
Denoted by Watts
How do you calculate Pressure, and what is its’s units?
Pressure = Force/ Area
Pascal (Pa)
What is static pressure?
Static pressure acts equally in all directions. It is denoted by a small “p” and measured in Newtons per square metre.
How do you calculate static pressure?
Height x density x gravity.
What is dynamic pressure?
Dynamic pressure acts only in the direction of the flow. It is denoted by a small q and is sometimes called “q” pressure.
How do you calculate dynamic pressure?
1/2 x density x v*2
What is static pressure denoted by?
Bar and measured in deca-Newtons per square centimetre.
What is 1 Bar equal to in Pascal?
100 000 Pascal.
What are sound waves the same as?
Pressure Waves
What is the speed of sound denoted by?
Small “a”
What is the formula for the speed of sound?
20 x Square root of Temperature
What is the constant in the speed of sound equation?
20
Is the speed of sound is lower at high altitudes?
Lower because the temperature is lower.
What is the pressure wave known as when an aircraft hits Mach 1?
Shockwave
How is Mach calculated?
Speed of the aircraft/ Speed of sound.
What are the three sound regions which are de ned by the Mach numbers?
Subsonic
Transonic
Supersonic
What speed is included in the Transonic region?
Critical Mach Number to Mach 1.3
What layer of the atmosphere has clouds and rain and many different weather conditions?
Troposphere
What is unique about the stratosphere in regards to temperature?
Temperature does not change as the altitude increases.
What height is the Tropopause over the poles?
8km
What height is the Tropopause over the equator?
16km
What does ISA stand for?
ICAO Standard Atmosphere
Who created the standard atmosphere?
ICAO
What is the standard altitude for the Tropopause?
11km
How is the change of temperature calculated in the stratosphere?
There is no change in temperature in the stratosphere
How are density and pressure impacted by altitude
The density and pressure gradually decrease with altitude
What is the standard temperature of the tropopause?
-56.5 Celsius
Under standard conditions what does the temperature vary with at increasing altitude?
6.5 celsius per km
