Aero Science Flashcards
SI UNITS
- length
- mass
- time
- m (meters)
- kg (kilograms)
- s (seconds)
Units - temp
C (Celsius) or K (Kelvin)
- 0C = 273K
- a change of 1C = a change of 1K
Derived units - Force
Measured in Newtons (N), where 1N is the force required to accelerate 1kg of mass at 1ms^-2
Derived units - pressure
Measured in pascals (Pa), where 1Pa = 1N per m^2
Non SI units - horse power
1HP = 746 W
Non SI Units - speed
Measured in kts, where 1kt =
- 0.514m/s
- 1.85km/h
Non SI Units - navigational distance
Nautical miles (nm), where 1nm = 1852m
Non SI Units - altitude
Feet (ft), where 1ft = 0.3048m
Derived units - Power
Measured in watts (W), watts are equivalent to Nm/s, Power = W/t
Scalar vs vector quantities
- scalar only has magnitude/size e.g temp
- vector has both magnitude + direction
How are vector quantities represented
By a vector arrow with its length representing magnitude and the arrow head representing direction
Vector addition/subtraction with multiple vectors acting in the same direction
Simply combine head to tail to produce resultant
Combining vectors acting in different directions
Drawing them with the tail of one vector connected to the to the head of the other
The resultant is the vector that can be drawn from the tail of the first to the head of the last
Combining vectors originating from the same point
Resultant can be found by drawing a parallelogram, the resultant is formed by the diagonal that goes from the start point of both vectors to the interception point of the parallelogram
Resolving single vectors
Any single vector can be resolved into 2 components that are at right angles to each other (note: components can be drawn in any direction as long as the vector is within the right angle)
Trig functions
Describe the relationship between vectors and their components, they represent the ratios between lengths of sides of a right angle triangle
- sine (sin)
- cosine (cos)
- tangent (tan)
Trig function equations
- sin🌀 = O/H
- cos🌀 = A/H
- tan🌀 = O/A
Trig functions small angle
If less than 15• , the cos of the angle is very close to 1 so for practical purposes H=A
Describing motion
- speed = distance traveled/time taken (is a scalar quantity)
- velocity = distance travelled in a given direction/time taken (is a vector quantity)
- acceleration occurs when there’s a change of velocity (can be direction and/or speed change)
Newtowns first law
Every object continues in its state of rest or uniform motion in a straight line unless acted upon by an external force
Inertia
Is the tendency of an object to continue moving at a certain velocity (or to remain at rest with 0 velocity)
What does inertia depend on
Solely on mass, so the larger the mass the larger the force required to overcome its inertia
Mass
The amount of matter in an object
Force
Tends to move the object out of its state of rest or uniform motion in a straight line, a net force must be available to cause acceleration
Newton’s second law
The external force acting on a body is proportional to the products of its mass and acceleration production by the force (F = ma)
Hectopascal
Used to measure atmospheric pressure, where 1hPa = 100Pa
Weight
Is the force produced when a mass is acted upon by gravitational attraction, measured in N (whereas mass is measured in kg)
Weight equation
W = m x g
g = is the acceleration due to gravity (and for masses on/near the earths surface g = 9.81ms^-2)
‘g’
1’g’ = normal acceleration of gravity
2’g’ = means acceleration that is x2 gravity and a person subjected to 2’g’ will feel twice as heavy as their normal weight
Momentum
= mass x velocity
It refers to the difficulty of stopping a moving object or changing its direction of travel
Newtons third law
For every action there is a opposite and equal reaction
Work
Work is done when a force moves an object through a distance (W=Fxd), its measured in Nm or J (1J = a force of 1N moves an object 1m)
Power
Is the rate at which work is done
Energy
Is the capacity to do work (measured in J) it comes in various forms such as
- KE = 1/2mv^2 (energy due to motion)
- potential energy (is the energy of position e.g gravitational potential energy)
Moment
It is a turning force about a pivot/turning point (turning force is also known as torque or leverage)
- m = Fxd (where distance is arm length)
- measured in Nm (or kg-mm)
Couple
Consists of 2 equal but opposite parallel forces, when the forces of a couple act around a midway point torque is produced
CG
Centre of gravity (or centre of mass) - the weight of an object acts through its CG, if an object is suspended from its CG or point directly above, it will balance and not rotate, however, if the suspension point/pivot point is displaced horizontally from the CG a moment will exist and the object will not balance
Translational equilibrium
An object in a state of rest or constant velocity is said to be in equiibrium (as the sum of all forces acting upon it is 0 so no net force will exist to cause acceleration
Rotational equilibrium
Occurs when object is either rotating a constant velocity or not rotating at all, theres no angular acceleration and the sum of all moments acting on the object is 0 (so if torque exists in one direction it is balanced by toque in the opposite direction)
