2.2 Mechanics - Statics (Lvl 2) Flashcards
What is force?
Is an interaction which tries to change a body state of rest or uniform motion in a straight line.
Its a vector quantity.
As force is a vector, what does it have?
Both magnitude and direction.
What is Moment?
A turning effect produced by a force acting at a distance with respect to an object fulcrum.
What is the formula for moment?
M = F x s
M = moment (Nm) F = force (N) s = perpendicular distance (m)
How do moment and torque differ?
moment is used for static applications and torque used for dynamic applications.
What are opposing moments?
They are total moments that act against each other and are applied at points separated by a distance.
What is the formula for opposing moment?
M1 = F1 x s1 and M2 = F2 x s2
M1 (2) = anticlockwise (clockwise) moment (Nm)
F1 (2) = force on the left (Right) hand side of the fulcrum (N)
s1 (2) = perpendicular distance from the fulcrum (m)
What does the term “the principle of moments” mean?
If the total clockwise moment about any axis equals the total anti-clockwise moment about the same axis, the body will be in balance.
What is a couple?
A pair of forces that are equal in magnitude and opposite in direction, applied at points separated by distances perpendicular to the forces
(tap wrench).
What is the formula for couples?
T = F x s T = F x r x 2
T = Torque applied by a couple (Nm) F = One of the forces (N) s = distance between the forces (m) r = radius (m).
What is a scalar quantity?
Quantities that have magnitude but no direction.
What is a vector quantity?
Quantities that have magnitude AND direction, acting in a straight line.
What is the effect that results from two or more vectors of the same type of quantity acting on an object known as?
Resultant.
When using the Pythagoras method to calculate the resultant, which length is the resultant?
The hyptoenuse.
What other methods can you use to calculate the resultant?
The Pythagoras Theorem and parallelogram method.
When using the parallelogram method to calculate the resultant, which length is the resultant?
The diagonal of the parallelogram.
What is centre of gravity?
An imaginary point through which all the weight of an object is said to act of on object.
What is stress?
A quantity that describes the magnitude of forces that cause deformation.
What is stress also known as?
Strain.
What always accompanies stress?
Strain.
What is the formula for stress?
Stress = Force/ area.
What 5 basic forms of strucural stresses are aircraft subjected to?
- Tension
- compression
- shear
- bending
- torsion.
What is strain?
The deformation of a material due to stress.
What is the result of a strain calculation?
A ratio.
What is the formula for strain?
strain = change in length/ original length.
What is elasticity?
The ability of a material to return to its original shape once external forces have been removed.
What is the opposite of elasticity?
Plasticity.
What is plasticity?
Ability of a material to changes its shape permanently when subjected to stress.
The materials remains deformed after the force applied has been removed.
What is tension?
Stress being applied which tends to increase the length of the body.
What is tension sometimes to referred as?
Axial or normal stress.
What does hooke’s law states?
That the extension of an elastic object is directly proportional to the force applied to it.
What is the formula for hooke’s law?
Force = spring constant x extension.
What can the elastic limit be referred to as?
Proportional limit.
What is the elastic limit?
The point at which permanent deformation occurs and the elastic region ends.
After the elastic limit, which does a material then enter?
The plastic region.
When a small increase in force is applied in the plastic region, what happens deformation of the object?
A large amount of deformation.
What is the constant known as youngs modulus?
The ratio of stress and strain that is a constant since hooke’s law applies.
What is the formula for youngs modulus?
Youngs modulus = stress/strain
What is compression?
A force applied which tends to shorten or squeeze a body.
What is the compressive strength of a material measured in?
N/m^2.
What is shear stress?
Where it tries to slice a body apart by sliding one layer over another.
What is bending?
A stress that comprises of both compression and tension on a matieral simulatenously.
What is torsion?
Applied to a material when it is twisted.
What other forces does torsion use?
Compression and tension.
How do compression and tension forces apply in torsion stress?
Diagonally across the body, with the one force acting at a right angle to the other.
What is hardness?
Tendency to resist indentation.
What is strength?
Tendency to withstand an applied load without failure or plastic deformation.
What is toughness?
Tendency to resist breakage when deforming or when impact forces applied to a material.
Wahat is brittleness?
Tendency to break without change of shape.
What is vapour?
A gas that can be liquefied by an increase in pressure without decreasing its temperature.
What is volatile?
One which readily evaporates at normal temperature.
What is flammability?
Where a material will ctach fire readily.
What is flash point?
The temperature at which a liquid will catch fire when exposed to a naked flame.
What is toxicity?
How poisonous a susbatnce is.
What is inert?
Where a substance will not chemically combine with another substance.
What is pressure?
A force applied to the surface of an object.
What is the formula for pressure?
Pressure = force / area.
What is atmospheric pressure?
The force exterted by the weight of the atmosphere.
What happens to the density of air with altitude?
Air density decreases.
What is the average atmospheric pressure at sea level?
14.7 psi.
What is the most common barometer?
Mecury barometer.
What can effect the accuracy of a mecury barometer?
The ambient temperture as mecury expands with an increase in temperature.
What is gauge pressure?
The amount of pressure by which the measured in a fluid exceeds that of the atmosphere.
What is ambient pressure?
The pressure in the area immediately surrounding an object.
How is absolute pressure measured?
Relative to the absolute zero pressure meaning the pressure that would occur at absolute vacuum.
What is the formula for absolue pressure?
Absolute pressure = gauge pressure + atmspheric pressure.
What does Archimedes principle state?
A body in a liquid will be subject to an upward force equal to the weight of liquid it displaces.
What is the force called in Archimedes priciple?
Bouyant force.
Where may bouyant forces be pressure?
Liquid and gases.
If bouyant forces exsist in gases, how does a hot air baloon rise from the ground?
The air is heated making it less dense than the air they displace.
What is it meant by positive bouyancy?
The bouyant forces is more than the object weighs, causing the object to float.
What is it meant by negative bouyancy?
The bouyant force is less than the object weight, causing it to sink.
What is meant by neutral bouyancy?
When the objects weight is equal to the weight of the fluid it displaces.
How would you calculate how high or low an objects float?
Comparing the densities of the body and fluid.
What is the formula for calculating how high or low an object floats?
Ratio = density of body / density of the fluid.
What is meant by torricellian vacuum?
Where the weight of the mecury creates a vacuum at nearly zero absolute pressure in the top of the tube.
