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.
����
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.
�����������
F1D1 = F2D2.������� �(where F is each force, and D is the distance each force is from the pivot point)
Schilt, C. R. (2007). Developing fish passage and protection at hydropower dams. Applied Animal Behaviour Scence, 104, 295-325.
The biomechanical principle stability for a pirouette is primarily concerned with the center of mass
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.
A connecting rod subjected to an axial load F may buckle with x-axis as neutral axis in the plane of motion of the connecting rod, {or} y-axis is a neutral axis. The connecting rod is considered like both ends hinged for buckling about x axis and both ends fixed for buckling about y-axis. A connecting rod should be equally strong in buckling about either axis [8].
Then it flows in a generally southerly direction and forms the boundary between Arizona and the states on Nevada and California. Near Yuma, Arizona, the river crosses the international border into Mexico and flows for about 145km (90 miles) to its mouth on the Gulf of California. The River Colorado drains parts of 7 states, a total area in Colorado, Wyoming, Nevada, Utah, Arizona, New Mexico and California, of about 626,800sq km. What controls / how have people controlled the flow ?
This is an ineffective tow due to the fact that the patient is not on top of the swimmer, my technique for the strides are correct. However if I was to correctly align my centre of buoyancy with the patient it would be more of an effective tow. By doing so it would prevent further drag and resistance, the amount of water displaced caused more eddies to form creating a suction affect. Overall my performance for the timed tow proved inefficient causing the patient to be submerged under water at some stages, positive aspects of the tow are the correct grip and strides.
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 is achieved when the diver takes the first leap into the air with his arms raised. When he comes back down on the board, his own mass falling onto the board will apply a certain force. An additional force is added as the arms swing down at the same time with a greater acceleration, applying more force. At the bottom of the diving board's oscillation, all of the now stored potential energy is released. The diver swings his arms upward and begins to release his pressure on the board. The board pushes the diver up and into the air with a huge force.
In analyzing the force associated with a certain spring, whether it is in you pen or under your truck, Hooke’s Law applies.
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.
WEATHERFORD, G.D. BROWN, F.L,. (1986) New Courses For The Colorado River, Albuquerque, N.M., pp. 25 3.
Floatation devices teach improper swimming techniques. Whether the floatation device is a lifejacket or a pair of arm floaties, a child will not learn the proper way to swim with the aid of these devices. Life jackets are created with the sole purpose of keeping someone’s head above the water. Life jackets do not allow for a swimmer to be horizontal in the water. Learning to swim in a vertical position not only leads to doggy paddling instead of swimming, but also often causes the child to learn to be afraid of putting their face in the water. While arm floaties do allow for the swimmer to be horizontal in the water, they add artificial buoyancy to the child. This causes the muscles needed for floating without these devices to not develop. The child often learns to move forward in the water, but not how to stay above the water.
Sufficient length of string was attached to the hanger so that the free end wraps once round the axle of the flywheel. 5. The mass was winded up to an appropriate height. 6. Verified that the string fell off the axle when the mass hit the ground.
lines, rope, and plastic nets are being caught in the rutter and the engine, but
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.