M2.2 Flashcards
What does an atomic number denote
Number of protons
What does atomic mass consist off
Protons and neutrons
What is fluid resistance
It occurs when a solid object travels through a liquid or gas, or when a liquid travels through a solid. This causes resistance to motion within the fluid
What is viscosity
It’s the measure of a fluids resistance to flow
What happens to a liquids viscosity if temperature increases
The viscosity of a liquid decreases rapidly with an increase in temperature. Whereas a gas increases with an increase in temperature
What is a vibration
Refers to the mechanical oscillations about an equilibrium point
What is a desirable vibration compared to an undesirable vibration
Necessary for correct functioning of various devices like a loud speaker. But undesirable as it could be an imbalance like an unbalanced wheel
What is free vibration
When a mechanical swing is set off with an initial input and then allowed to vibrate freely at its natural vibration unless it damps down.
Forced vibration
When a continuous vibration or motion is applied to a mechanical system. The frequency of the vibration depends on the force applied. Whereas the amplitude (height) of mechanical system
What is a harmonic
Harmonics are periodic frequency’s. Repeats itself at standard intervals. Can be described as sinusodual with constant amplitude.
Does a harmonic wave have a positive frequency
Yes. Harmonics have a positive integer followed by fundamental frequency’s - the lowest frequency in the periodic wave.
What is a fundamental frequency
One wave that doesn’t change its integer. The first harmonic of a harmonic series.
What is the equation for a wavelength of an harmonic
Wavelength = 2 divided n (index of harmonics) x length of the body
What is resonance
The tendency of a system to oscillate at a maximum amplitude when applied force equal or at its natural frequency.
What is velocity ratio
It’s how far the effort (force push or lift) has to move in relation to the load.
If the object has a velocity ratio greater than 1 then the distance moved by the effort is greater than the distance moved by the load.
What is the equation for velocity ratio
Velocity ratio = sin (distance in) divided sin sout (distance out)
What is mechanical advantage
The ratio of the force produced by a machine to the force applied to it. Used to access performance.
What’s the equation for MA
MA = resistance(N) divided Effort (N)
What is actual mechanical advantages (AMA)
The ratio of output over input. shows how much easier work can be done.
AMA = F out divided F in
What is ideal mechanical advantages (IMA)
Shows what would exist if there was no friction on machine.
IMA = sIn divided sOut (s being distance)
What is a first class lever
The fulcrum is located between the effort and the resistance (load). FLE. middle.
Increasing distance from effort to the resistance (load) increases advantage provided by lever. When effort is applied it acts in the opposite direction to resistance. Oppositing moment either side of fulcrum.
E x L = R x L
What is a second
Fulcrum is at one end of lever and effort is applied at opposite end - wheelbarrow. The mechanical advantage is the same with 1st and 2nd lever. Only difference is the resistance and effort on first class lever act in same direction.
Third class lever
Always at the end with effort in the middle and load at the end. Landing gear attaches to aircraft which acts as a piviot point.
Inclined planes
A plane surface inclined to a horizontal plane at any angle but a right angle. Advantage as it allows large resistance to be moved yet small effort.
F1 x S1 = F2 x S2
What is a pulley
A wheel which rope or chain is pulled in order to lift or lower a heavy object.
What is the mechanical advantage of a single pulley
1
What is the effort required to raise an object
Weight of object
What is a gear
Multiple single gears working together to alter the relation between speed and direction of a mechanism.
What is a drive gear
The one that drives the driven gear to produce angular velocity and torque.
What happens when drive and driven gear have have same amount of teeth
No mechanical advantage MA = 1
How do you find mechanical advantage
MA = Fout divided Fin. load divided by effort. Driven gear divided by drive gear
What is Newton’s first law?
States that a body will remain at rest or continue to move with a uniform velocity unless acted upon a force
What is force?
It is a vector quantity, so it has both magnitude and direction
Which gear turns quicker
The smaller gear
What is a moment?
A moment is a turning effect produced by a force acting at a distance with respect to an objects fulcrum, causing a body to rotate about a point
To work out the revolution ratio do you swap them around to what it would be for a gear ratio
Yes for a gear ratio it would be 2:1 but for revolution it would be 1:2
What are opposing moments?
They are total moments that act against each other against each other and are applied at points separated by distance
What is the equation for opposing moments?
M1=F1 x S1
What is a spur gear
Has their teeth cut straight across and are used to connect two parallel shafts. When both gears have external teeth shafts turn in opposite directions. Whereas if both need to go in same direction one must have internal teeth.
What is a couple?
A pair of forces that are equal in magnitude and opposite in direction, the combined moment of the forces produces a torque on the object they act on
What is stress?
it is the quantity that describes the magnitude of forces that cause deformation. Deformation is also known as strain.
What is stress always accompanied with
Strain
What is a bevel gear
Teeth cut into a convivial surface. Two gears mesh together to transit power between two shafts at an angle to each other. If gears are not parallel then a bevel gear is used.
What is elasticity?
The ability of a material to return to original shape once external forces have been removed
What is a worm gear
Has a toothed wheel worked by a short revolving cylinder called a worm. A screw thread. The worm is the driving component. Used for large reduction in speed. Hoisting machines
What is hookes law
Force equals spring constant times extension F=K x e
What is shear strength
Tries to slice a body by sliding one layer away from another
What is hardness?
The ability to withstand scratching and indentation
Examples of hard materials
Diamond, cast iron
What is a sun and planet gear
Input drive is the sun gear. Planet gear held together by a cage and driven around by sun gear. Then engages at fixed ring which does not rotate. Used when small spaces
What is strength?
The ability to withstand an applied load without failure or deformation
Materials with strong strength?
Steel, Titanium
What is toughness?
Tendency to resist sudden impact force
What is brittleness?
Tendency to break without change of shape
What are brittle materials
Concrete, cast iron, glass at room temp
What is efficiency
The ratio of work which is transferred to a useful form, compared to total input work.
n = MA dividend VR x 100
n = Wout divided Win x 100
What is elasticity?
Tendency to return to original shape when the force distorting a material is used
What are elastic material
Hard steel, rubber
What is plasticity?
Tendency to remain in shape when the distorting force is removed, some very hard substances are also plastic
Examples of materials with plasticity
Lead, gold, putty, plasticine, wet clay
What is malleability
Is the tendency to undergo compressive stress without damage. Malleable materials can be beaten, rolled or pressed into shape without fracture
Malleable materials
Red hot steel, aluminium
What is Newton’s first law
Every object that remains at rest stays at rest unless acted upon by an external force. The law of inertia
What is Ductility
Tensile strength without damage, used for making of wires
Ductile materials
Copper, gold, silver
What is a volatile liquid?
A liquid that readily evaporates at a normal temperature
What are examples of volatile liquids
Petrol, ethanol, methylated spirits
Difference between a flammable and inflammable substance
There is no difference they’re both the same
What is a flash point?
The temperature of a liquid which it will catch fire when exposed to a naked flame
What is Newton’s second law
Force = mass x acceleration
What is an inert substance
One which won’t chemically combine with another substance
Examples of inert substances
Helium, neon, argon
What is Newton’s third law
Every action has an equal and opposite reaction.
Equation for pressure
P = f/ A
What is mass
Amount of matter in a body
What is absolute pressure
Atmospheric pressure plus gauge pressure
A force in which pushes a body up when in a fluid is known as what
Buoyancy
What happens to an object when it is heavier than the buoyant force
It will sink
What is the natural unit for mass
The mass of protons and neutrons
What is linear movement
Uniform movement in a straight line
How do you work out mass
Mass = weight divided by gravity 9.81m/s3
What is a centripetal force
A force that wants to move into the middle. E.g a hammer thrower with a hammer
What is weight
Weight of a body is the gravitational force of attraction between the mass of earth and mass of body. Weight decreases as body is moved away from earths centre
What is inertia
The property of matter that causes it to resist any change in its motion in either direction or speed. Newton’s first law. Greater mass greater inertia
What is work
The force causing a movement or displacement of an object
W = F x S (distance) w[F]
What is power
Measures the rate at which work is done
Power = work divided Time P[w]
What is energy
The capacity to do work
What is mechanical work
The energy held by a body after work has been done. Kinetic and potential. [1j = 1w]
What is potential energy
Energy a body has due to position or condition allowing to do work after realised.
Ep = m x g x h
What is kinetic energy
Energy a body has due to its motion. The work needed to accelerate a body of mass from rest to a velocity.
Ek = 0.5mv2
What is total energy
The sum of all different forms of energy in a system. Energy can’t be created or destroyed. Total energy will stay the same
What is chemical energy
Energy that is stored in chemical bonds between atoms. A form of potential energy
What is heat
The renal energy due to kinetic energy and potential. Also called internal energy. Often created when converting energy due to temperatures.
What one out of the three frictions has the highest friction
Starting friction
What is friction
The force resisting relative motion of materials rubbing together
What’s the difference between starting friction and sliding friction
Starting friction has a higher friction as it requires a application of an initial force to get it moving
How’s specific gravity measured
With a hydrometer
What is momentum
A vector quantity that described mass in motion. Any object that moves has momentum. The more momentum and object has the harder it is to stop.
What are the two variables of momentum.
Mass and velocity
What’s the equation for momentum
P = m x v
What is it meant by the conversion of momentum
In a closed system it’s the total momentum before event and is the same after. Not effected by external forces
E.g collisions and explosions as it’s one reaction.
What is collision
Occurs when two bodies interact with one another, leading to a transfer of kinetic energy and momentum. Kinetic energy may change but total momentum stay same
What are the two types of collision
Elastic collusion - kinetic energy is conserved
Inelastic energy - kinetic energy is not conserved
What is static pressure?
Pressure which is everywhere, works in addition to dynamic factors so are present at the same time
What is dynamic pressure?
Pressure that emerges from velocity of the fluid in motion
What is the equation for collision
M1V1+ M2V2 = M1V1 + M2V2
What is total pressure?
Is the sum of dynamic and static pressure
As static pressure decreases, dynamic pressure…..?
Increases
Velocity—— dynamic pressure——-….?
Kinetic energy
What is impulse
A force that changes the momentum of a body over a period of time . J =F x T
What is a Venturi tube?
A tube that is narrower in the middle than the ends
What is a gyroscope
It’s an instrument that contains a disc called a rotor, rotating about an axis at a high speed.
What are the two properties of a gyroscope
Rigidity and precession
What does rigidity mean
It’s the application of Newton’s first law of motion. The ability of a gyro to retain its axis in a fixed direction in space unless acted upon by external forces.
What is rigidity effected by
Rotor mass
Speed of rotation
Bearing friction
Effective radius that mass acts on
What is precession
An external force that is applied to change the direction of the rotor spin axis. The gyro resists this and moves at right angles to the direction applied.
What are gyros used for
Used as a device to measure or Martian orientation and angular velocity. Provides stable datum for aircraft.
How many gimbals gives a gyro a full rotation
Two gimbals
