Unit 6 - Oscillations and Mechanical Waves Flashcards
Example of simple harmonic motion
Masses on springs and pendulum systems
What is the one major things that systems in simple harmonic motion have
Resotring force
What is a restoring force
A force that wants to return the system to eqbm (opposing what you want to do to it)
In a simple harmonic oscilator the resotring force is proportional to
Proportional to the ammount of displacment in the system
What is the equation connecting the force exerted by a spring, the spring constant and displacement
Fs = -kx
Force is proportional to …. but not ….
Acceleration but not velocity
Max displacement AKA
Displacement
Period (T) is
The time taken for an entire cycle to occur
Cos starts at
MAX amplitude (1)
Sin starts at
Minimunim amplitude (0)
x(t) = (2)
A cos (wt) or A sin (wt)
What is w
2pi / T
x(t) = (in terms of time period)
A cos ((2pi/T) t)
OR
A sin ((2pi/T) t)
What is the effect of a change in amplitude on the peirod in a spring system
There is no effect
T (for a spring)
2pi X root of (m/K)
m = mass k = spring constant
90 deg –> RAD
pi/2 rad
2 pi rad –> DEG
360 deg
What is the effect of adding a phase constant inside of the sine term
Shift the graph to the left in the negative x direction
What is the effect of subtracting a phase constant inside of the sine term
Shifts the graph to the right
What is the effect of changing the mass on a pendulum in terms of a pendulum
No effect on time period
T (for a pendulum)
2pi x root (L/g)
L = length g = gravitational acceleration
Define a mechanical wave
Distrubance through space which usually transfers energy
What is a longitudinal wave
Waves where the direction of disturbance is in the same direction as the wave is travelling
What is a tranverse wave
A wave where direction of energy transfer is perpendicular to the direction of energy transfer
What is a wave pulse
Single period of a wave
What is amplitude
From the resting point to the peak of the wave
What is the period of a wave
TIme taken for a complete wave cycle to occur
What is frequency
The number of cycles that occur per second
Equation for frequency
f = 1/T
Wavelength is
the distance travelled after one period
Velocity -
Wavelenght/period
Wavelength X frequency
Sound travles as
A wave
What is the only way to alter the speed of sound
Change tge prperties of the medium that it is travelling through
What is the equation for the velocity of a sound wave through a given medium
V = ROOT (B/P)
What is B
Bulk moduls
An increased __________ almost always overides an_____________
Bulk moduulus //// Increase in density
What type of air does sound travel faster through - why?
Faster through hotter air since hotter air is less dense
Facts about ultrasound
20000 Hz
Reflected when it reaches a change in medium
Reflection detected by a transducer which calcuates time between initiation and return
Distance is calculated to produce a 3D image
How can you produce a CLEAER image from ultrasound
Higher freq and shorter wavelength so there is less diffraction
What is the Doppler ffect
The apparent change in the freuqency of a wave based on relative motioon between the source of the wave and the observer
What happens if the source of the wave is travelling at the same speed as the observer
Sonic boom - all waves arise at once
What be observed if you move towards the source
Higher freq since more wave crests reach per second
What would be observed if you move away from the source
Lower freqeuncy since fewer wave crests reach per second
Fobs =
Fs . ((Vw+Vobs)/Vw)
Where does wave interference occur
Where waves overlap in the same region
Superposition says that
You can find he total wave by addiing together the contributing waves
Constructvie interference
Forms a much bigger wave
When two waves are in phase or are spaced a distance apart that is an integer number of the wave lengths
Destructive interfence
Forms a much smaller wave
When two waves are out of phase or a spaced at a distance which is not an integer multiple of the wavelengths
In standing waves
ANTINODES are
NODES are
Antinodes points with most motion
Nodes points with least motion
In standing waves wavlength =
2L/N
L = length N = nodes
What is the equation for wavelngth in a tube where one end is open
4L/N
Beat frequency is where
Waves have different frequencies
What is the equation of Beat freuqnecy
FB = modulus of F1-F2
