3/27/2014 Master Ithttp://www.webassign.net/v4cgi/questions/tutorial_popup.tpl 1/2Master ItTo measure her speed, a skydiver carries a buzzer emitting a steady tone at 1 800 Hz. A friend on the groundat the landing site directly below listens to the amplified sound he receives. Assume the air is calm and thespeed of sound is independent of altitude. While the skydiver is falling at terminal speed, her friend on theground receives waves of frequency 2 247 Hz. (Use 343 m/s as the speed of sound.)(a) What is the skydiver's speed of descent?(b) Suppose the skydiver can hear the sound of the buzzer reflected from the ground. What frequencydoes she receive?Part 1 of 4 ConceptualizeSkydivers typically reach a terminal speed of about 150 mi/h (~75 m/s), so this skydiver should also fallnear this rate, unless she is wearing an outfit with an unusual drag coefficient. Since her friend receives ahigher frequency as a result of the Doppler shift, the skydiver should detect a frequency with about twice theoriginal Doppler shift.Part 2 of 4 CategorizeWe can use the equations for the Doppler effect to find both the skydiver's speed of descent and thefrequency she hears reflected from the ground.Part 3 of 4 Analyze(a) The sky diver source is moving toward the stationary ground,so we haveSolving for the speed of the skydiver, we findWith v = 343 m/s, f = 1800 Hz, and f' = 2250 Hz, we findPart 4 of 4 Analyzef ' = f ,vv − vdiver1 − = .vdivervff 'vdiver = v 1 − .ff 'vdiver = v 1 − = 343 m/s 1 − = 68.2 m/s.ff ' 1800 Hz 2250 Hz3/27/2014 Master Ithttp://www.webassign.net/v4cgi/questions/tutorial_popup.tpl 2/2(b) The ground now becomes a stationary source, reflecting crests with the frequency at which they reach theground, and sending them to a moving observer. Since the waves are reflected, and the skydiver is movinginto them, we haveFinalizeThe answers appear to be reasonably consistent with our predictions. The Doppler effect is used to find thespeed of many different types of moving objects, like raindrops (with Doppler radar) and cars (with policeradar). Radar uses electromagnetic waves instead of sound waves;; the Doppler shift equation has asomewhat different form for electromagnetic waves than for sound waves.f '' = f ' = f = 1800 Hz = 2690 Hz.v + vdivervvv − vdiverv + vdiverv343 + 68.2 m/s343 − 68.2
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