In late June each year, wild Alaskan sockeye salmon begin to migrate up the Broo

Question

In late June each year, wild Alaskan sockeye salmon begin to migrate up the Brooks River in Alaska. Their eventual aim is to reach the spawning grounds in the upper reaches of the river or along Lake Brooks above. Consider the migration of one such fish with a mass of 5.8 kg. It travels a distance of 2.2 km in the river, increasing its elevation by 15 m. To achieve this, it propels itself along at a constant velocity underwater, experiencing a constant drag force of 3.5 N. During its travels, the salmon encounters Brooks Falls. To proceed upstream it must leap out of the water, jumping a height of 1.1 m. (a) Using energy considerations only, calculate the minimum take-off speed that the salmon needs to enable it b) Calculate the amount of energy required for the salmon to change its elevation as it proceeds upstream. (c) Similarly, calculate the amount of energy that the fish must expend to overcome the drag force as it swims (d) Supposing the fish can convert internal energy into work with an efficiency of 15%. Accounting for both to jump up the falls. Explain any assumptions you make. Ignore the extra energy required to make the leap up the falls. along the river change in elevation and the drag force, how much internal energy is needed for the fish to swim up the river?

Explanation / Answer

part a:

minimum take off speed be such that when it reaches the maximum height , it will have zero velocity.

then all the initial kinetic energy is converted to potential energy

let speed be v m/s

then 0.5*mass*speed^2=mass*g*height

==>speed=sqrt(2*g*height)

=4.6433 m/s

part b:

amount of energy required to change its elevation =0.5*mass*speed^2

=62.524 J

part c:

energy to overcome the drag force=force*elevation

=3.5*15

=52.5 J

part d:

total energy required=62.524+52.5

=115.02 J

then internal energy needed=115.02/0.15

=766.83 J

Related Questions

Navigate

• Browse (All)
• Browse I
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.