Chinook salmon are able to move through water especially fast by jumping out of

Question

Chinook salmon are able to move through water especially fast by jumping out of the water periodically. This behavior is called porpoising. Suppose a salmon swimming in still water jumps out of the water with velocity 6.23 m/s at 42.9° above the horizontal, sails through the air a distance L before returning to the water, and then swims the same distance L underwater in a straight, horizontal line with velocity 3.91 m/s before jumping out again.

(a) Determine the average velocity of the fish for the entire process of jumping and swimming underwater.
m/s

(b) Consider the time interval required to travel the entire distance of 2L. By what percentage is this time interval reduced by the jumping/swimming process compared with simply swimming underwater at 3.91 m/s?
%

Explanation / Answer

for projectile motion

range = Vo*costheta*T1

T1 = L/vo*costheta = L/(6.23*cos42.9) = L*0.22

for swimming

T2 = L/V = L/3.91 = 0.26 s

average velocity = L+L/(T1+T2)

Vavg = 2L/L*(0.22+0.26)

Vavg = 2/0.48 = 4.17 m/s    <<----answer

++++++

(b)

total time for jumping / swimming = T1+T2 = 0.48L

total time for swimming 2L = 2L/3.91 = 0.51L

percentage difference = (0.51L-0.48L)/0.51 = 5.8 % <<--answer

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