Crocodile Copley

After finding this video on YouTube, our group was curious as to how difficult running and playing two didgeridoos would be. Bryant Smith helped us to understand the level of difficulty.



As seen on the video, Bruce Copely really enjoys running with the didgeridoo. Thus, Bruce Copely sets out on his daily run with the didgeridoo that emits a whine of 256 Hz. He is running at a speed of 10 miles per hour (4.47m/s) and he overtakes a lady who is strolling at a speed of 2 miles per hour (0.89 m/s). What is the frequency observed by the lady walking when Bruce Copley is approaching her from behind, and what is the frequency observed by the lady walking after Bruce Copley passed her?

Before Copley passes her we would use the equation:
f(obs)=f(source)[(1-vobs/vsound)/(1-vsource/vsound]

f(obs)=256[(1-0.89/343)/(1-4.47/343)]

f(obs)= 258Hz

After Copley passes her we would use the equation:
f(obs)=f(source)[(1+vobs/vsound)/(1+vsource/vsound]

f(obs)=256[(1+0.89/343)/(1+4.47/343)]

f(obs)=253Hz

Principles to Note: the before observed frequency is going to increase whereas the after observed frequency is going to decrease in comparison to the actual source frequency.


Just in case Copley ever comes across any dangerous crocs while he is running, he knows exactly what to do with them....