posted by Savannah .
The figure below shows a general situation in which a stream of people attempt to escape through an exit door that turns out to be locked. The people move toward the door at speed v = 4.1 m/s, are each d = 0.30 m in depth, and are separated by L = 1.75 m. The arrangement in the figure occurs at time t = 0.
(a) At what average rate the layer of people at the door increase?
(b) At what time does the layer's depth reach 4.1 m?
a person gets to the door each 1.75/4.1 seconds. So depth increases .3m each time.