Question

A model airplane traveling at 5 m/s approaches you. The frequency of the hum produced by the motor is 652 Hz. Assume the speed of sound to be 342 m/s. What is the observed frequency of the hum?

Answer 1

Here's the equation you want to use:\[f _{O}=\frac{ c }{ (c \pm v _{S}) }f _{S}\]where c is the speed of sound in the medium (342 m/s); vS is the speed of the source; fS is the frequency of sound emitted by the source; and fO is the frequency heard by the observer. If the source is moving away from the observer, vS is positive, and if the source is moving toward the observer, vS is negative. That should give you everything you need.

Answer 2

Thank you!