The Physics of Dip Netting
Introduction to Dip Netting
Dip netting for salmon in the Copper River is a lot of fun but is also a lot of work.� During the summer months salmon will leave their home in the ocean and travel upstream in the Copper River to spawn in its many tributaries.� Near the small town of Chitna the Copper River flows through a narrow canyon which greatly increases the speed of the river.� This makes it harder for the salmon to swim upstream.� However the canyon also creates back eddies near the shore in which the river will actually flow the opposite direction.� This is good and bad news for the salmon.� Good news because the back eddies are flowing the direction the salmon want to go which makes their trip a lot easier.� And bad news (from the salmons point of view of course), it makes the salmon easier to catch because the water is flowing the ideal direction for dip netters as shown in the pictures below.
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Notice that the back eddie makes it really easy for the dip netter.� If there was no back eddie the current would push the net the other direction, which makes dip netting a lot harder.
The Physics
The physics of dip netting is really quite simple.� All a person has to do is find a back eddie with a nice constant current and hold the net underwater in the hopes a salmon will swim into it.� The physics then becomes a static equilibrium problem which means that none of the parts are moving in any way either in translation or in rotation (applies only to reference frame used) (Halliday 307).� This is illustrated in the picture below.
The dip net pole can be compared to a lever of class 1 and the lever principle can be applied, similar to the applet at http://www.walter-fendt.de/ph11e/lever.htm.� As stated in the applet from the Contemporary College Physics Simulation Library a lever is in balance if the total left side torque is equal to the total right side torque.� Applying that statement to the picture above the person must apply a much greater force on the pole in order to maintain torque equilibrium because the distance from the pivot point is much less than the distance from the force of the current to the pivot point.� This can be expressed mathematically.
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F1D1 = F2D2.������� �(where F is each force, and D is the distance each force is from the pivot point)
The warm, slow-moving waters created by the dams are ideal living conditions for the pike minnow that were found to be eating the hatchlings. A bounty was created for catching the pike minnows, creating additional funds that must be spent in order to encourage the salmon to survive. Fish transportation was also implemented to move the salmon 130 miles upstream past the dams.
Slingshot diving fin comes with some innovations such as Gear Shift, Mid-foot Flex Joint, and Power Bands, which are specially designed to provide a great experience while diving. Power Bands are equipped with a pure silicone that provides a boost of energy on the power stroke and reduces fatigue. That allows you accumulate energy and reclaim it prior to the upstroke rather than wasting your energy like with some other diving fins.
Torque= Force x radius , since the radius is half the diameter , T=F x D/2
With smiles on our faces we cast our wisely selected lures into the ocean, but we then encountered our first problem of saltwater fishing. Our lures wouldn’t sink. As soon as they hit the water, the ocean current would just buoy them to the surface and, soon after, down current into the line of a nearby fisherman. Improvising our rigs, we dug the heaviest weights out of our tackle boxes and clamped them onto our lures. Sure enough, we got our lures underwater and under control.
counterweight is hoisted up as high as possible it has lots and lots of potential
I predict that the further I pull the band back the further it will ‘fly’. This is based on the fact that the more tension involved means that the potential energy is greater therefore the kinetic/moving energy will also be greater.
Generation after generation gathered food off the land, people are continuing to practice this in our modern world today. Societies expressly continue to gather their own food as it provides an inexpensive, delightful tasting meal. One of the techniques of our historical past that is still in use today, that has been used for generation after generation is “netting” fish. Netting is a classic technique that has not faced as many revisions to its practice. It persists from one generation to the next due to the fact, that many do not understand it to be harmful to the environment; others may enjoy the idea of letting commercial fisheries catch large numbers of fish as it continues to keep some of Americans favorite meals low cost. Devastating fall out from neglectful thinking about netting will occur in the future if preservative action toward this way of life is not taken. Minimizing the use of nets in waterways will ensure salmon and other fish survive for many more generations to come, allowing this plentiful food source given to us by Mother Nature to be exploited and enjoyed by our future kin. With food sources now readily available, fishing with nets should be reevaluated as follows; who is allowed to fish with nets, what are their purposes, and how will this effect tributary fishing populations.
The thing that is easiest for everybody to learn while fly fishing physics is the arm movements. We probably all know the basics for the most part right? You pull the rod back then have your arm do a throwing motion and then stop and then send the fly flying right? Well that’s it for the most part but there is still more to learn with arm movements. In the magazine Fly Fisherman there was an article that gave a great tip. Their tip is “Try not to move your arm or wrist like a windshield-wiper blade. Instead, your
This leads to those fish becoming endangered and even extinct. For example, "up to 2,000 of the animals were drowning in gill nets in the Gulf of Maine each year--enough to eventually wipe out the species” (Cone). Some species can’t reproduce fast enough to continue having a stable population. This leads to endangerment and eventually extinction. In addition to this, "the vaquita... become entangled in nets set for the totoaba, and drown" (Malkin). Aquatic animals, such as the vaquita, are being over caught and killed in nets that weren’t even meant for them. Most of the anglers don’t even use the vaquita that was unintentionally caught. On the other hand, "...fish is the primary source of protein for one in six people on earth” (Whitty). To stop using drift nets to collect fish would deny many people much needed foods. Even so, "Erik Anderson, who has fished New England's waters for 30 years, would haul up his gill net and occasionally discover a harbor porpoise, entangled and dying, trapped in the mesh along with his harvest of cod and flounder" (Cone). Although some people may have to find a different source of protein, the demise of drift nets will save entire
Nick looked down into the clear, brown water, colored from the pebbly bottom, and watched the trout keeping themselves steady in the current with wavering fins. As he watched them they changed their positions by quick angles, only to hold steady in the fast water again (472).
This force now can be used by the diver not only to go up, but to rotate and therefore perform various dives.
In analyzing the force associated with a certain spring, whether it is in you pen or under your truck, Hooke’s Law applies.
12. Twisting the wings to raise or lower the leading edges can also affect the boomerang's performance.
Fishing contains a wide variety of physics. when you cast you are using projectile motion and rotational motion. when you hook a fish it will often use the drag from the current agenst you. Immagine draging a fish through a swift current. You deal with the tention of your line, and the friction of the line through the guides. you also deal with friction when you use a drag.
Why doesn’t it just get stuck in between the two opposing forces at its equilibrium point? To answer that, we need to break one of the forces down into its components. Since the tension force is always perpendicular to the path of motion, we will break down gravity. It consists of one component that is in the direction of the acceleration of the bob (Fgrav-tangent), and another that is directly opposite that of the tension force (Fgrav-perp), as seen in the free- body diagram below. The gravity vector is always the sum of these two vectors.