Wave Basics Or, How to Destroy a Slinky Without Even Trying… AP – Ch 16 & 17

MT KNOTES Counts 20% of FINAL GRADE! MG + 3/5 SA ANY block except 5 & 7 LAST Open-Note Exam of year. NO CURVE.

Shtuff Topics left – Waves & Sound (Current) MidTerms – Electricity – Review & AP Exam

Basic Terminology Simple Harmonic Motion (SHM) – Anything that vibrates with periodic motion – Has an equilibrium position – Obeys Hook’s Law

Basic Terminology Wavelength Wavelength – DUH! – Displacement of a sinusoidal periodic wave along the independent coordinate. – i.e. The length of the wave. ‘ ’.

Basic Terminology Pulse Pulse – Single disturbance – ½ Pulse

Basic Terminology Period – Time required for one complete wavelength. – ‘T’ – Unit - Seconds

Basic Terminology Frequency Frequency – # wavelengths per second – f = 1/T – Unit – 1/sec, sec -1, Hz (Hertz)

Basic Terminology Amplitude Amplitude – Disturbance along the vertical. – Height of wave as measured from x-axis A

Phase Shift

Text p288

Basic Terminology Velocity of waves?

Energy in SHM Just like anything else:

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LAB 25 Following are old, & I mean OLD, pix of the LAB. Please, no silly comments about being a poor photographer or the ‘retro’ look…

LAB 25 OLD Camera Stuff.

MT KNOTES Counts 20% of FINAL GRADE! MG + 3/5 SA ANY block except 5 & 7 LAST Open-Note Exam of year. NO CURVE. Monday PM Review

MT KNOTES Topics 1.2-D Kinematix (Projectile) 2.FMA 3.MV & E 4.Circles 5.Gravitation (L &  interspersed…)

KNOTES AP EXAM #5 – WHEN? [24 hr period] ~20 MG & 1/2 SA – Waves

Figure 2 4.What does a specific point on a slinky do as a pulse goes by?

How many pencils?

Figure 5 6.What is observed when two similar pulses (same amplitude) are sent down the slinky, one from each end, oriented in the same direction, at the same time.

7.When pulses are generated from each end, do they pass through or reflect back from each other? They pass through each other.

Figure 4 The superposition of two equal and opposite pulses on a coil spring. In the fifth picture they almost cancel each other.

Less Into More Dense Material When a pulse is sent from the end of a slinky, what is observed?

More Into Less Dense Material When a pulse is sent from the metal end of a slinky, what is observed?

Superposition

Types of waves Transverse

Types of waves Longitudinal (Compressional)

Types of waves Surface (Water)

Superposition

Waves -Advanced Stuff Tighten your seatbelt… It’s getting’ bumpy!

Advanced Wave Stuff SHM – Follows F=-kx

Advanced Wave Stuff SHM – Follows F=-kx

Advanced Wave Stuff SHM - Energy

Advanced Wave Stuff SHM – T & f -

Advanced Wave Stuff SHM – T & f

Advanced Wave Stuff SHM – T & f

Advanced Wave Stuff SHM – Pendulumaeii

Types of waves Transverse

Types of waves Longitudinal (Compressional)

Types of waves Surface (Water)

Earthquake (Rayleigh W)

Standing Wave A wave that reflects on itself…

Wave reflection

Advanced Wave Stuff Fundamental f’s

Ch16 STOP HERE…

Ch 17: Sound

Advanced Wave Stuff SHM – Resonance – V sound Demo

Advanced Wave Stuff SHM – Resonance – V sound Demo

Advanced Wave Stuff Sound Intensity – Logarithmic Function (HUH?) –  =10 log I/I o I o = 1 x W/m 2 Chart pg 475

Intensity I (W/m 2) Intensity  (dB) Threshold of human hearing 1 x Leaves rustling1 x Whisper1 x Normal 1 m 1 x Inside closed car1 x Car w/o muffler1 x Live rock concert 1120 Pain10130 Taylor Mad1 x BELLS

Decibel (dB) Scale This scale is a logarithmic scale used for measuring the intensity of sound. The threshold of hearing is assigned a sound level of zero decibels. Intensity (W/m 2 )Intensity (dB) 1 x x x

Decibel (dB) Scale Intensity Intensity (W/m 2 ) (dB) 1 x threshold of hearing 1 x normal breathing 1 x average whisper (2m) 1 x empty theatre 1 x residential area-night 1 x quiet restaurant 1 x person conversation 1 x busy street traffic 1 x vacuum cleaner

Decibel (dB) Scale Intensity Intensity (W/m 2 ) (dB) 1 x loud stereo 1 x concert hall 13 th row 1 x pneumatic chisel 1120max level rock group 10130threshold of pain 1 x military jet taking off 1 x wind tunnel 1 x instant breaking ear drum

A log excursion…

Beats WaWa sound produced with 2+ sounds of close f’s.

External Site Beat 330Hz +

Advanced Wave Stuff Sound Intensity Problems? – One sound produces a  1 = 90dB and another is  2 = 93dB. What is the ratio I 2 /I 1 ?

Advanced Wave Stuff Doppler Effect? – Occurs when a sound or an observer moves in the direction of the sound! (Say WHAT?) Sirens, Moving cars, Planes… Resonance tube Demo Tuning Fork Demo

Ugly Doppler Math

= Apparent Frequency = Actual Frequency = Object’s Velocity = Source Velocity = Sound Velocity TOP Sign = TOWARD

Apps & Probs A little pot-bellied kid is standing in the waves unattended. He notices 10 waves crash against his little chubby legs in 2 minutes. What is the frequency of these ocean waves?

Apps & Probs Two boats are hanging out 10 meters from each other. As the waves go by, one boat is at max up while the other is max down and no crests are between them. What’s the wavelength of the water waves?

Apps & Probs A boat is anchored. Over the side is a rope ladder with rungs one foot apart and there’s 8 of them visible above the waterline. The tide comes in and rises at a rate of ½ foot per hour. After 5 hours, how much of the rope ladder is still visible above the waterline?

DUH!

Apps & Probs The wavelength of a sound in air is 20 o C. What is its wavelength if it enters fresh water at 20 o C?