Oscillations And Waves Flashcards
Simple harmonic motion
Constant indefinite oscillation
Equilibrium position
Aka natural position
When the spring is neither stretched or compressed
The point at which the net force is zero
Hooke’s law
force= -( spring constant k) * ( position)
The greater the value of k the stronger the spring is
Direction of spring force is always opposite position
Part of SHM
Elastic potential energy of SHM
= 0.5 * spring constant k* ( position^2)
When we stretch the spring the spring stores energy that is released as kinetic energy once we let go of the spring
Kinematic of SHM
An oscillation is aka a cycle which is one round trip
A period is the amount of time to complete one cycle
T=1/ frequency
T= 2pi[sqroot( mass/ spring constant )]
Frequency is the amount of cycles that occur in one second
f=1/ period
Simple Pendulums
There is no friction at the suspension point during oscillations
String of the pendulum has negligible mass
Displacement taken as an angle
Restoring force is gravity or mg sin theta
Period= 2pi(length of pendulum/ gravity)
Waves
= a disturbance in a medium that transfers energy from one place to another
Transverse waves:
Created by wiggling a long rope
Wave moves horizontally even though the rope is moving up and down
Wave travels perpendicularly to direction medium is vibrating
Wavelength aka the length of one cycle is the distance between two peaks
Amplitude is the maximum displacement
Wave speed= wavelength* frequency
Wave speed of transverse wave=sqroot( tension/ linear density)
When a wave passes into another medium its speed changes but it’s frequency doesn’t
Changing frequency doesn’t change wave speed but wavelength
Interference of waves
When two or more waves are superimposed on each other they will combine to form a resultant
In phase when crest meets crest and trough meets trough
Constructive interference
Amplitudes add
Whole cycle referred as 2pi radians or 0 degrees or 360 degrees
Out of phase when crest meets trough
Destructive interference
Amplitudes subtract
Whole cycle referred as pi radians or 180 degrees
If waves aren’t exactly in or out of phase then amplitude of resultant will be between difference and sum
Standing waves
When there is two waves on rope( the original wave plus th reflected wave) with same frequency and amplitude but in opposite directions. These waves will interfere and the resultant wave no longer travels ( standing waves)
Each point along the rope has its own amplitude and the points that don’t vibrate up and down are nodes
Antibodies are halfway between a set of nodes
First harmonic:
1 wave, 2nodes
Wavelength = 2* length of rope
Second harmonic:
2waces, 3nodes
Wavelength= (2*length)/2
Standing wavelength for two fixed ends
Wavelength = 2* length/ harmonic number
Harmonic number= nodes-1
Frequency =(harmonic numberwave speed )/ 2 length
