1. Wave Motion Chapter 16

2. Mechanical Waves Source : disturbance - disturbance makes medium vibrates (up/dn, side/side) Medium (water, air, string,…) Mechanical Wave: periodic (sine/cosine) disturbance traveling through a medium b/c motion of hand is sinusoidal, wave is sinusoidal also We do not care about the wave. We care about medium’s element displacement (sine wave ) y(x,t)

4. Energy Transfer By Wave Motion Disturb (drop a stone, speak,…) a medium (water, air,…) Disturbance is energy Disturbance creates a wave that transfer energy from A to B Medium matter (water, air, string,…) dose not transfer - elements oscillate around their equilibrium positions perpendicular to wave propagation: transverse wave parallel to wave propagation : longitudinal wave

5. Traveling Wave On Stretched string

6. General Form of a Traveling Wave If a wave does not pass through zero at t=0, it has a phase shift Phase shift has angle unit Can be determined from initial conditions : t=0,x=0

7. Wave speed and particle speed wave particle

10. Examples A traveling wave passes a point of observation. At this point the time between successive crests is 0.2 sec. Which of the following is true a) λ=5cm, b) f=5Hz, c) v=5m/sec, d) λ=0.2 cm, e) not enough info 2. One end of string 6m long is moved up and down with SHM at f=60Hz. The wave reaches the other end of the string in 0.5 sec. Find λ of the wave on the string 3. The wave function of a harmonic wave on a string is a) In what direction does this wave move and what is its speed. b)find λ, f, T of the wave. C) what is the maximum speed of any string segment

11. Wave Speed on a Stretched String

13. Waves Carry Energy Waves transport energy through medium as they propagate Hand performs work on the end of string by moving it up and down. Energy enters the string and propagates along its length.

14. Energy and Power of A Traveling Wave Along a String Mechanical Wave transports KE and elastic PE(EPE) along string Continuous energy supply requires a continuous source for waves Each string element ‘dm’ and length ‘dx’ is provided with KE and EPE by tension forces KE depends on the element velocity: velocity is max at y=0, velocity is zero at y=A EPE depends on element stretch: stretching is max at y=0, and zero at y=A Power P avg is the rate of energy transmission

16. Chapter16 Assignment 16.5, 7, 9, 11, 20, 30, 39,47, 53, 55