Question

A robot vacuum cleaner emits ultrasonic frequencies at 40 kHz while cleaning the carpet. The robot vacuum cleaner is moving in a straight direction. Your old, adorable dog sees the robot vacuum cleaner and starts walking away at 0.1 m/s. The speed of sound in air is 343 m/s.

A) If your dog can hear sounds up to 45 kHz, what is the minimum speed the robot vacuum cleaner must ​go in the same direction​ so that the dog cannot hear it.

B) If your dog can hear sounds down to 67 Hz, what is the minimum speed the robot vacuum cleaner must ​go in the opposite direction​ so that the dog cannot hear it.

C) Assess the reasonability of your answers to parts 1 and 2. Will you ever have to worry about your dog hearing the robot vacuum cleaner?

Answer 1

formula was used.