Swimming Up River

    Five species of Pacific salmon are found in the Copper River system and delta regions.  All of these species are anadromous, or hatch in freshwater and move to saltwater before returning to freshwater to spawn.  Sockeye salmon and King salmon migrate the farthest up the Copper River to spawn. 



                                                                              *www.fws.gov/coleman/ images/salmon.jpg

In order for these salmon to swim up the river, or against the current, the salmon must be able to swim faster than the current that pushing them in the opposite direction. 

Vsalmon  > V current

If a salmon is swimming in a straight path up the river to its native spawning grounds with a velocity of 0.5 meters/second and increases its velocity to 1.1 meters/second in 20 meters, we can determine the acceleration of the fish during this time.  We assume that the current does not change its velocity, therefore we can ignore its velocity relative to the salmon (who we treat as a particle). 

Using the kinematics equation:    Vfinal^2  =  Vinitial^2 + 2a (xf - xi)
    we can solve for the acceleration as the change in the squared velocities over 2 x(distance traveled).
                           a =  (1.1)^2  -  (.5)^2    =  0.048 m/s^2
                                   2 ( 20 meters)




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