Question

How fast should the platform move, vp, for the person to detect a beat frequency of 7.00 hz ? take the speed of sound to be 344 m/s. express your answer numerically in meters per second using three significant figures. hints?

Answer 1

Delta(f) =f0 * v_rel/c , where v_rel is the relative velocity between source and observer. The source is moving at a speed v but the sound bounced off the wall and the receiver is moving toward it too. So, Delta(f) = f0 (2 V) / c Hence V = c Delta(f) /(2 f0)= 344 m/s * (7.00Hz/(2*245Hz)) =4.91 m/s