2.2.1 - Mechanics (Statics) Flashcards
What is the SI unit for mass?
the kilogram (kg) or slug
What is 1 slug in kg?
1 slug = 14.59kg
What is 1lb in N?
1lb = 4.448N
What is the difference between mass and weight?
An object’s mass is a quantity of matter making it up; which will never change.
An object’s weight is a measure of the gravitational force exerted on it (which changes depending where it is in the universe)
What is the formula for weight?
W = mg
What is 2.2lbs in kg?
2.2lbs = 1 kg
What is 1kW equal to in BTU?
3412 BTU/Hour
What is the numerical value for gravitational force?
9.8
What is the equation for moment?
Moment = Force x distance
What does the sum of clockwise moments equal?
The sum of anticlockwise moments
What is a couple?
A pair of forces acting in equal but opposite directions (eg, a steering wheel)
What is Sin(90)?
1
What is the equation for torque?
t=F x d x sin(ϴ)
How do you calculate the scale reading on a torque wrench when using an extension?
Scale reading = Specified torque x (length/length + extension)
What is a Centroid?
The centre of mass of an object.
What are the three aircraft weighing methods?
- Weighbridge Scales
- Hydrostatic Weighing Units
- Electronic Weighing Equipment
How many readings should be made when weighing an aircraft?
2
What are the two categories of quantities in physics?
Vectors and Scalars
What is a vector?
A quantity that is fully described by both magnitude and direction
What is a scalar?
A quantity that is fully described by magnitude alone
What is strain?
A measure of the deformation of a material under a load. The ratio of the amount of deformation to it’s original size.
What are the two primary structural stresses?
Tension and Compression
What is tension?
A primary stress that tries to pull a body apart (a weight on a chain)
What is compression?
A primary stress that tries to squeeze parts together (a weight on a post)
What is shear?
Forces that try to slide a body apart.
What is torsion?
A twisting force. Tensile stress acts diagonally across a structural member that is twisted.
What is bending?
A bending force tries to pull one side of a body apart while at the same time squeezes the other side together.
What is the formula for stress?
Stress = Force/Area
What is Hooke’s Law?
F=Ke
(K being the spring constant)
(e is the extention)
What is the elastic limit?
Where Hooke’s Law does not apply. It is known as the limit of proportionality.
Permanent deformation occurs after this limit.
What is the formula for strain?
Strain = Deformation/Original length
What is the Bulk Modulus?
It gives the change in volume of a solid substance as the pressure on it is changed.
What is Poisson’s Ratio?
The ratio of transverse strain to the axial strain.
When a member is stressed in tension, it’s length increases (axial strain) and it’s width decreases (transverse strain).
What is the equation for density?
Density = Mass / Volume
What is the equation for pressure?
Pressure = Force / Area
What is 1Pa?
A Pascal (1N of force on 1M^2).
1/100,000Bar (incredibly low pressure)
What is an Isobar?
A line on a weather map joining together places of equal atmospheric pressure.
What is Pascal’s Law?
Any force applied to a contained fluid is transmitted in all directions throughout the fluid and at right angles to the containing surfaces.
What is the formula for the pressure on an object submerged in a fluid?
P = pgh
What happens to pressure with increasing depth in a fluid?
It increases
What is Archimedes’ Principle?
A body immersed in a fluid is buoyed up by a force equal to the weight of the displaced fluid
What is the formula for Pressure on an object submerged in a fluid?
Pressure = p (rho) x g x h
(rho is density of fluid)
What is the formula for the volume of a sphere?
V = 4/3 pi x r^3
The unit of Young’s module are that of…
Pressure
What is the height of mercury required to give 1 bar?
760mm (1 bar is almost atmospheric pressure)
For the CGS (centimetre-gram-second) system, what is the force?
The ‘Dyne’ - which produces an acceleration of 1cm/s^2 for a mass of gram
What is the opposite of a tensile force?
Compression (tension is to be pulled apart)
What is the difference between a tied gyro and an earth gyro?
Both are free to rotate in 3 axis, both have a fixed point but an Earth gyro is specifically ‘tied’ to an earth reference point
What is the coefficient of limiting friction?
The point at which an applied force overcomes friction and an object begins to move
