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2024 Tahsili Physics: Waves and Sound
Periodic Motion
Periodic Motion 
motion in which the restoring force is directly proportional to the displacement (springs and pendulum) 
Hook's Law 
states that the force required to compress a spring by a distance is proprtional to the distance 
Hook's Law Equation 
F = kd (k is the spring constant) 
PE of a spring 
PE = 1/2 x k x d^{2} 
application of a simple pendulum 
to determine the gravitational acceleration 
Periodic Time 
T = 2(pi)√(L/g) 
Mechanical Waves
Transversal Waves 
waves that oscillate perpendicularly to their direction of motion 
Longitudinal Waves 
waves that oscillate in the same direction as their motion 
Surface Waves 
waves that move perpendicularly and parallel to the direction of motion 
One dimesional wave 
ex: Rope 
Two dimensional Wave 
ex: water waves 
Three dimensional waves 
ex: sound and EM waves 
Doppler Effect
Doppler Effect 
the change in frequency produced by a moving source with respect to an observer 
Doppler Effect Formula 
fo = fs(v±vo / v±vs) 
vo is positive if the observer moves towards the source 
vs is positive if the source moves away from the observer 


Waves
Mechanical Wave 
a wave that requires a medium to translate in 
Electromagnetic Wave 
a wave that does not require a medium 
Amplitude 
the maximum displacement from the equilibrium position 
Periodic Time 
the time needed to complete one full cycle 
Frequency 
the number of cycles completed in one second 
Frequency Formula 
f = 1/T 
Wavelength (λ) 
The distance between two crests or troughs 
Wavelength Formula 
λ = v / f (v is the wave speed ) 
The energy carried by a wave is directly proportional to the amplitude squared 
Standing Waves
standing waves 
a combination of two waves moving in opposite directions, while having the same amplitude and frequency 
Nodes 
positions on a standing wave where the wave stays in a fixed position due to the destructive interference 
Antinodes 
positions on a standing wave with the highest amplitude 
the number of nodes are always greater than the number of antinodes 
Sound Waves
Sound wave 
a longitudinal wave composed of compressions and rarefactions, and whose speed is directly proportional to temperature 
Loudness 
depends on amplitude 
Pitch 
depends on frequency 
Sound Intensity 
the relative sound intensity compared to a specific standard intensity expressed in decibels 
humans can hear noises between 20 Hz and 20,000 Hz 
Standing Waves in Air Columns
Formula for two open ends (antinodes are greater) 
λ = 2L / n (n is the harmonic level) 
Formula for a closed column (nodes = antinodes) 
λ = 4L / n (n is the harmonic level) 

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