1. The problem statement, all variables and given/known data Two kids are positioned as in the following figure and A emits a long sound. d=100m, x=40m, vsound=340m/s How long (t) does the sound emitted by A has to be such that B perceives a signal that lasts 2t? 2. Relevant equations 3. The attempt at a solution Seems like an easy problem. I don't understand what do we mean by "long sound", and what does it mean that a sound lasts t seconds. Does this mean that A can hear the sound for t seconds and B has to hear the sound for 2t seconds?