1. The problem statement, all variables and given/known data A siren emitting a sound of frequency 1000 Hz moves away from you towards the face of a cliff at a speed of 10 m/s. Take the speed of sound in air to be 330 m/s. a. What is the frequency of the sound you hear directly from the siren? b. What is the frequency of the sound you hear reflected off the cliff? c. What is the beat frequency between the two sounds? 2. Relevant equations f(BEATS)=f1-f2 The Doppler Effect f'=f((v(air)+-v(detector))/(v(air)+-v(source))) 3. The attempt at a solution The beat frequency is easy, but I am confused on how to use the Doppler Effect equation (i.e. which signs to use, etc). Thanks for the help!