The beat detected on a moving platform.
A speaker fixed to a moving platform moves toward a wall, emitting a steady sound by a frequency of 215Hz. A person on the platform right next to the speaker detects the sound waves reflected off the wall and those emitted with the speaker.
How fast must the platform move, vp, for the person to detect a beat frequency of 2.00 Hz?
Take the speed of sound to be 344 m/s.