"A flood crest" Can take years to travel from its initiation point to the mouth of a river. Is the maximum stage of the river at any point along the stream from a flood event. Is when a stream overflows its normal flow channel and spills out onto the floodplain. Usually increases downstream from the area covered by the rain storm.

It may seem strange that the selected velocity does not depend on either the mass or the charge of the particle. (for example, would the velocity of a neutral particle be selected by passage through this device? ) the explanation of this is that the mass and the charge control the resolution of the device--particles with the wrong velocity will be accelerated away from the straight line and will not pass through the exit slit. if the acceleration depends strongly on the velocity, then particles with just slightly wrong velocities will feel a substantial transverse acceleration and will not exit the selector. because the acc