Doppler Effect and Sonic Booms Physics Tiffany Rhodes

STATIONARY SOURCE • A Bug Jiggling in Still Water = Fixed Position • Same Speed, wavelength and frequency in all directions • A and B experience exact same frequency!! • In Sound, both hear the same Pitch, the actual pitch!

Stationary Source

MOVING SOURCE • Bug Swimming at same speed • A and B experience different • • frequency! A = Lower Frequency B = Higher Frequency Moving away = low pitch Moving Toward = high Pitch

Moving Source http: //www. lon-capa. org/~mmp/applist/doppler/d. htm

DOPPLER EFFECT http: //www. youtube. com/watch? v=imox. Dcn 2 Sgo http: //www. youtube. com/watch? v=Pew. Ifsxy. ORE

Doppler Effect Explained http: //www. youtube. com/watch? v=i. N 3 f. O 5 l 4 Rww http: //www. youtube. com/watch? v=FQq. CSpf 2 v. LA

Doppler Effect Explained with MATH • • • F’ = perceived frequency Fo = actual frequency V = speed of sound Vs = Speed of source + use when source is moving away from observer - use when source is moving toward observer

SONIC BOOMS • Break through the ‘pile up’ of waves • Overlapping wave crests disrupt the flow of air over the wings, making it harder to control the craft.

Moving Same Speed as Sound • Now the source is moving at the speed of sound in the medium • (vs = v, or Mach 1).

Who was the person to break the sound barrier? • What was the type of plane that he used to break the sound barrier?

Chuck Yeager was the first person to break the sound barrier when he flew faster than the speed of sound in the X-1 rocketpowered aircraft on October 14, 1947

Moving Faster than Speed of Sound Supersonic • It is this intense pressure front on the Mach cone that causes the shock wave known as a sonic boom as a supersonic aircraft passes overhead

Mach 1 supersonic

Shock Wave – increase in pressure

Shock Waves • Subsonic – sound waves reaching our ears are perceived as one continuous tone • Supersonic – sound waves overlap to reach listener in a single burst - increase in pressure is like the sudden expansion of air produced from an explosion

Supersonic on the Ground

Airplane Facts The Lockheed SR-71 Blackbird is, to date, the fastest airplane ever to streak across the sky, even though it's more than 30 years old. Capable of speeds over 2200 mph -- that's more than 3 X the speed of sound -- the SR-71 can fly at altitudes above 80, 000 ft.

Sonic Boom (Breaking the Sound Barrier) http: //www. youtube. com/watch? v=u. Q 2 pkm. ISOLM http: //www. youtube. com/watch? v=OEmi. TYt. W 5 cs http: //www. youtube. com/watch? v=CF 7 h 3 Ew. BPjc&NR=1 http: //www. youtube. com/watch? v=w. Hrwg. Rs. X 0 BI http: //www. youtube. com/watch? v=Nii. E 26 Udcq. Y http: //www. youtube. com/watch? v=r 91 O 3 Z 3 i. Vp. Y

Sonic Booms Reviewed http: //www. lon-capa. org/~mmp/applist/doppler/d. htm http: //www. youtube. com/watch? v=-d 9 A 2 oq 1 N 38

Make sure you are keeping up with your work. Finish Worksheets Pg 353 top#1 -2, bottom of page #1 -2 pg 355 #1 -3 Pg 389 #1 -3 Pg 390 #1 -2 Read Pages 386 -393 Pg 406 -407 # 48, 59

Mach Number Physics CP 1 Tiffany Rhodes Chapter 12

Mach Number • What do you already know about Mach Number? Related to sound? ? Related to air planes? ?

Mach Number • Relates speed of object with speed of sound • Usually used with aircrafts since they are our fastest means of travel • Mach Number = Speed of Object/ Speed of sound • Speed of object and sound have to have same units. They cancel out… • Mach Number has No units!

What do you know about an airplane that travels at mach 1? • It is traveling at the same speed of sound What do you know about an airplane that travels at mach 2? l It is traveling double the speed of sound

II. Wave Equation • Sound is a wave so therefore the wave equation still applies. • Speed of the wave = wavelength * frequency • V= *f

Questions • Mach Number problems? • Wave Equation problems?

Warm Up A rocket is traveling at 8643. 6 km/hr. If the air temperature is 20ºC, what is the rocket’s Mach Number?

Answer • Speed of object = 8643. 6 km/h • Speed of sound = 332 + 0. 6* Temp = 332 + 0. 6 (20) = 344 m/s Convert to km/h 344 m 1 sec 1 km 3600 sec 1000 m 1 h = 1238. 4 km/h Mach # = Speed of Object/Speed of sound = 8643. 6/ 1238. 4 =7