Kinetics - Definitions Flashcards
Motion
Continuing change of position
Uniform acceleration
Motion caused by constant acceleration
Uniform circular motion
Motion of an object in a circle at a constant speed
Centripetal force
The force necessary to keep an object moving in a curved path and is directed inward to the centre of rotation
Centrifugal force
Force equal to centripetal force but acting In the opposite direction
Pendulum
A weight suspended in the earths gravitational field which is free to pivot at its top end
Angular amplitude
Angular displacement from rest to max swing position
Oscillation/vibration
One full swing to and from maximum position
Amplitude
The angle between one side and the other side during an oscillation
Damping forces
A decrease of vibrations as a result of removing energy through resistance to motion, reducing the amplitude if an oscillation
Vibration
Mechanical oscillations about an equilibrium point
Length of pendulum
Distance from the pivot to the centre of gravity of the Bob
Cycle
The motion completed in one period
Frequency
Number if cycles completed in unit time
Free vibration
Occurs when a mechanical system is set off with an initial input and then allowed to vibrate freely eg, tuning fork
Acoustics
Field of science related to sound and vibration
Forced vibration
When an alternating force or motion is applied to a mechanical system eg, washing machine, buildings during an earthquake and transportation vibration
Harmonics
Periodic vibrations that repeat at standard intervals
Fundamental frequency
The lowest frequency of a periodic waveform
Periodic time
Time taken to make one oscillation.
Resonance
The tendency of a system to oscillate at maximum amplitude at a certain frequency
Velocity ratio
The ratio of the distance moved by the point at which the effort is applied in a simple machine to the distance moved by the point at which the load is applied
Actual mechanical advantage (AMA)
The ratio of output force to input force
How much easier it is for the worker
Ideal mechanical advantage (IMA)
This is the mechanical advantage that would exist in an ideal world with no friction etc. It is the ratio of the input distance to the output distance
First class lever
A lever where the fulcrum is located between the effort and the load
Second class lever
A lever where the fulcrum is at one end and the effort is applied at the opposite end, eg a wheelbarrow
Third class lever
A lever where the point of effort is between the fulcrum and the load eg, a landing gear retracting mechanism
Inclined plane
A surface inclined horizontally at any angle but a right angle
Pulley
A wheel over which a rope or chain is pulled in order to lift or lower heavy objects
Fixed pulley
A pulley that does not change the amount of force applied but does change its direction
Moveable pulley
A moveable pulley increases the amount of force applied but does not change its direction
Block and tackle
A pulley system made up of a fixed and moveable pulley
Spur gear
Gear that has its teeth cut straight across their circumference and are used to connect two parallel shafts
Bevel gear
A gear that has teeth cut into a conical surface known as a pitch zone to transmit power between two shafts at an angle to each other
Worm gear
A gear consisting of a toothed wheel worked by a short revolving cylinder that has a screw thread on it
Sun and planet gear
The planet gears are in a cage and are driven around by the sun gear and engage at their outer fixed ring gear which does not rotate
Efficiency
The ratio of useful energy out to energy in
