River Definition and 196 Threads

  1. E

    River crossing and relative velocities

    Hi everyone, I've been having difficulties with this problem for a while. Here is my best attempt at solving it. If there's anything wrong, I honestly can't figure it out :). I would appreciate if anyone could go over it quickly and tell me if/what I did wrong. Homework Statement A boat...
  2. MarkFL

    MHB Round-Trip Speed Word Problem: Sarah's Boat & River Current

    Here is the question: I have posted a link there to this thread so the OP can view my work.
  3. L

    How Does a Rower's Speed and River Current Affect Crossing Time?

    Homework Statement A rower's maximum speed in still water is 6.0 ft/s. He decides to cross a 60 ft. wide river (at his maximum speed), with an apparent heading of 30° north of east. The river's current (relative to the ground) is flowing south at a speed of 1.0 ft/s. Find the rower's speed and...
  4. D

    Find the trajectory of a boat that moves in a river

    Homework Statement A boat part from the point P of the bank of a river, with width D, and that flows with a constant velocity VR, and moves with a constant velocity VB, directed towars a point Q, located on the other side of the river directly in front of P. If r is the instantaneous distance...
  5. jdawg

    What is the initial velocity of the second stone dropped into the river?

    Homework Statement A stone is dropped into a river from a bridge at a height h above the water. Another stone is thrown vertically down at a time t after the first is dropped. Both stones strike the water at the same time. What is the initial speed of the second stone? Give your answer in...
  6. S

    Max power plant output w/o killing river smelt?

    Homework Statement My simplified version of the equation: Power plant proposes output power increase from 188MW to 535 MW Excess heat is dumped into river with smelt. Smelt can withstand a 3.44C temp increase River = 222ft wide at dump site. Do not know depth or cross section here...
  7. N

    What Direction Should You Row to Cross a River Straight Across?

    Homework Statement You wish to row straight across a 63m wide river. You can row at a steady 1.3 m/s relative to the water, and the river flows at 5.7 m/s. In what direction should you head? How long will it take you to cross the river? The Attempt at a Solution Is the answer right? Could...
  8. G

    Maximizing Power Production on a River: Can We Meet Our Needs?

    Suppose along a river which is descending a mountain.On the river there are 10 hydropower stations A,B,C...J suppose at distances of 10km each.Now each station producees 100MW Power.So we get 1000MW. My Question is 'In this way can we produce as much power as we require by increasing number of...
  9. zoobyshoe

    50 ft. Rotating Ice Disk Forms in River

    http://www.theverge.com/2013/11/28/5154240/north-dakota-river-ice-circle-is-50-foot-wide
  10. C

    How Much Power Can Niagara Falls Generate with 90% Efficiency?

    Homework Statement The average flow rate in the Niagara River is 6.0 x 10^6 kg/s and the water drops 50 m over Niagara falls. If all this energy could be harnessed to generate hydroelectric efficiency at 90% efficiency, what would be the electric power output? Homework Equations P=mgh...
  11. P

    How Do You Calculate Average Speed in a River with a Current?

    Homework Statement A man can swim through still water 4.2m/s. Suppose this man swims in a river with current 1.3 m/s. Find his average speed over a trip: a) across the river and back b) a certain distance downstream and back The Attempt at a Solution a) Here is a diagram I made: Left side of...
  12. A

    A river flows with a velocity of 3 m/s east

    A river flows with a velocity of 3 m/s east. The river is 300 m wide. A boat is moving 10 m/s due north. If the river flow is not corrected for, how far will the boat have moved downstream by the time is reaches the far shore?
  13. M

    Calc problem with changing river velocity y=3sin(Pi*x/40)

    Homework Statement 40mm wide blood vessel. and flow is fastest in the middle of the vessel which is 3mm/sec. Blood flow speed is f(x)=3sin(pix/40) where x is the distance from the wall. and tumor cell on one side is swept into to blood and movies 5mm/s directly across the vessel. the tumor...
  14. W

    Relative velocity boat crossing a river

    Homework Statement A boat crosses river, 240 m wide,which flows parallel to the straight banks with velocity v1 = 12i, while the velocity of the boat relative to the river is v2 = 5j where v1 and v2 are measure in m/s (i) find the magnitude of the actual velocity of the boat. (ii) find...
  15. D

    Relative velocity/Boat & River Question

    Homework Statement 280m wide river, destination 120m upstream, river current is 1.35 m/s downstream and the boat speed in still water is 2.70 m/s. What should the boat's heading angle be (relative to the shore)? Homework Equations V_x = Vcosθ V_y = Vsinθ x = V_0 t (starting points set to 0...
  16. T

    What is the Correct Setup for River Relative Velocity Homework?

    Homework Statement Two students are canoeing on a river. While heading upstream, they accidentally drop an empty bottle overboard. They then continue paddling for 1 h, reaching a point 2 Km farther upstream. At this point they realize that the bottle is missing and, driven by ecological...
  17. T

    Relative velocity of river flowing

    Homework Statement A 400m wide river flows from west to east at 30 m/min. Your boat moves at 100m.min relative to the water no matter which direction you point. To cross the river, you start from a dock at point A on the south bank. There is a boat landing directly opposite at point B on the...
  18. M

    Hudson River accident. Friction on water

    Homework Statement I am in an introductory physics course. I am an aviation student, and we have to present on something related to our major. My group decided to go with an analysis on the Hudson River incident. I am trying to figure out the force of friction the water had on the...
  19. A

    Magnitude and Direction, Canoe on River

    Homework Statement A canoe has a velocity of 0.35 m/s southwest relative to the earth. The canoe is on a river that is flowing 0.65 m/s east relative to the earth. Find the velocity (magnitude and direction) of the canoe relative to the river. The Attempt at a Solution 0.930985 is the...
  20. P

    Two dimensional relative motion; boat and river problem

    Homework Statement Mary needs to row her boat across a 100-m-wide river that is flowing to the east at a speed of 1.0 m/s. Mary can row with a speed of 2.0 m/s. a) If Mary points her boat due north, how far from her intended landing spot will she be when she reaches the opposite shore? b)...
  21. L

    Relative Velocity Problem - Finding an angle of a boat going down a river

    Homework Statement A boat is capable of a constant speed of 4 m/s in a river that is flowing at 2 m/s. If the captain wishes to land 10m downriver while crossing a 50m river, then at what angle should the boat be aimed? Homework Equations...
  22. M

    River bank problem Need help ly

    River bank problem! Need help urgently! :( Homework Statement The water in a river flows uniformly at a constant speed of 2.50 m/s between parallel banks 80.0 m apart. You are to deliver a package directly across the river, but you can swim only at 1.50 m/s. If you choose to minimize the...
  23. G

    Cooling a pond with river water?

    Cooling a pond with river water?? Hi all, this is kind of a basic question and I am looking for a simple formula to use to illustrate how an idea is not practical. I worked almost this exact same problem years ago in a limnology class but can’t remember how I did any of it. I help manage a...
  24. J

    What is the force exerted on a paddle in a river in the following situation?

    If a paddle of area, A, is submerged in a river of water-velocity, v, and (assumed constant) water pressure, P, the paddle at an angle, m, what is the force exerted on the paddle by the moving water of the river? the paddle is being held still from a bridge...
  25. S

    Vectors - crossing a river w/ given flow

    Homework Statement a student want to cross a river flowing east at a rate of 2.0km/hr in a boat on the south bank and arrive at point L on the north (north and west) side. Point L is 0.5km to the left or west from the starting point (point K - point K is on the south side). Point L is 0.5km...
  26. T

    Calculating Distance and Time with two boats in a river

    Homework Statement Two boats, A and B, travel with a velocity of 4.90m/s across a river with a width of 72.9m. The river flows with a velocity of 2.50m/s. Boat A travels the shortest distance and boat B travels the shortest time. If both start at the same time, how much time will they take...
  27. I

    Entropy of the river due to coal heating

    Gamma (Cp/Cv) of a gas Homework Statement An experimenter adds 980 J of heat to 1.75 mols of an ideal gas to heat it from 10.0 C to 25.0 C at constant pressure. The gas does 234 J of work during the expansion. Calculate gamma (Cp/Cv) for the gas. Homework Equations Cv=Cp-nR Gamma...
  28. M

    Multivariable calc, boat moving on river functions problem

    Homework Statement there is a straight river 40m wide. the water speed on the river can be expressed as the function f(x)=3sin(∏x/40) If a boat is to cross the river from point a to point b at a constant velocity of 5 m/s determine the angle the boater should head. Homework Equations...
  29. S

    Relative velocity of river flow question

    Homework Statement A river is flowing 4.0 m/s to the east. A boater on the south shore plans to reach a dock on the north shore 30.0 Degrees downriver by heading directly across the river. What should be the boat's speed relative to the water? Also, what's the boat's speed relative to the...
  30. T

    Calculating Load Applied to Anchors Holding a Car in River

    Hi I am trying to work out the load applied to some anchors used to hold a car stationary in a man made river channel. I know it will be something to do with the surface area and the speed/volume of water. Can anyone help, admittedly I am a practical person not a acaedamic so layman terms...
  31. B

    How to Calculate the Angle for a Boat Crossing a River with a Current?

    Homework Statement A boat that can travel at 4.0km/h in still water crosses a river with a current of 2.0 km/h. At what angle must the boat be pointed upstream (that is, relative to its actual path) to go straight across the river? Homework Equations No equations were given but it...
  32. S

    Crossing a river ( relative velocity problem )

    Homework Statement A boat is crossing the river with a speed of 6.2 m/s east relative to the water. The river is flowing north at a speed of 2 m/s and is 750 m wide. a) What is the speed of the boat relative to the Earth? b) How much time is required to cross the river? c) How far downriver...
  33. N

    Trig Problem - Finding the width of a river

    [b]1. An observer is next to a river and wants to calculate the distance across the river. He measures the angle between his observations of two points on the shore, one on his side and one on the other side, the angle coming out to be 28º. The distance between him and the point that is on the...
  34. H

    Can 1,000 Boats Really Push the Chao Praya River Out to Sea Faster?

    There's a rather comical attempt being made in Bangkok to push the Chao Praya river out to sea faster using anchored/moored boats with the engines/props running. Here's a news clip: 1,000 boats to push flood waters October 11 BANGKOK: -- On October 11, a fleet of some 1,000 boats would...
  35. S

    Velocity of boat in river with varying current

    Homework Statement See attached. Homework Equations The Attempt at a Solution I originally began by assuming the rate was constant, obtaining the equations V_x^2 + V_y^2 = 1 \tan{\sigma} = \frac{V_y}{V_x} with the assumptions V_x(\sigma) = f(\sigma) V_y(\sigma) =...
  36. L

    Boat crossing river problem using reference frames

    Homework Statement A 110-m-wide river flows due east at a uniform speed of 3.3 m/s. A boat with a speed of 8.6 m/s relative to the water leaves the south bank pointed in a direction 37 degrees west of north. What is the (a) magnitude and (b) direction of the boat's velocity relative to the...
  37. K

    Question involving trigonometry & river currents

    1. A man points his rowboat north from A to B, straight across a river of width 100 m. The river flows due east. The man starts across, rowing steadily at 0.75 m/s and reaches the other side of the river at point C, 150 m downstream from his starting point. What is the speed of the river...
  38. D

    Underground River Found Under the Amazon

    http://www.msnbc.msn.com/id/44343669/ns/technology_and_science-science/t/underground-river-discovered-beneath-amazon/?gt1=43001" I had never heard of anything like this before, except in Journey to the Center of the Earth. Is this something that has been theorized for some time, or is it...
  39. J

    River flow on a planet or large object.

    So let's say we have a planet not too dissimilar in size to those in our Solar System. It doesn't have to be spherical. But let's say we want a river to flow round the object. We want the flow to last as long as possible. We can consider two cases seperately: in our Solar system...
  40. K

    Coriolis effect on a river flowing north-east?

    Homework Statement Consider a river of width 1000 m flowing 30 degrees east of north with a speed of 10m/s at latitude 50 degrees north. The river bottom is flat. On which side of the river is the water deeper and by how much?Homework Equations the only correction i need to use is -2m(omega...
  41. E

    A Horse Pulls a Barge in a River; What is the force of the water on the Barge?

    Homework Statement In the figure, a horse pulls a barge along a canal by means of a rope. The force on the barge from the rope has a magnitude of 7830 N and is at the angle θ = 18° from the barge's motion, which is in the positive direction of an x-axis extending along the canal. The mass of...
  42. E

    Kinematics - Boat over a constant River.

    Homework Statement A 400m wide river flows from west to east at 30 m/min. Your boat moves at 100m.min relative to the water no matter which direction you point. To cross the river, you start from a dock at point A on the south bank. There is a boat landing directly opposite at point B on...
  43. M

    How Wide Is the River Jean Camped Beside?

    1. Jean camps beside a wide river and wonders how wide it is. She spots a large rock on the bank directly across from her. She then walks upstream until she judges that the angle between her and the rock, which she can still see clearly, is now at an angle of 30 downstream (as shown in the...
  44. A

    Boat travelling in river without current

    Homework Statement This is a question from Gelfand's Algebra: A boat traveling upstream from A to B can cover the distance in a hours. The boat can travel downstream from B to A in b hours. How long would it take to travel from A to B if there was no current? The Attempt at a...
  45. S

    Bernoulli and flow in a flooding river

    Does the top of a flowing river curve convex because of Bernoulli's Principle? I was looking at a picture of a flooding river on Google Earth, and noticed that most of the debris was concentrated in a line down the middle of the river, corresponding to the area of most rapid flow. I know...
  46. E

    Tarzan swings across a river (centripical force)

    Homework Statement Tarzan tries to cross a river by swinging from one bank to another on a vine that is 10.0 m long. His speed at the bottom of the swing , just as he clears the surface of the river, is 8.0 m/s. Tarzan does not know that the vine has a breaking strength of 1.0x10^3 N. What...
  47. C

    Relative motion of a swimmer crossing a river

    A swimmer can swim at 2.0 m/s in still water. She attempts to swim due north across a river flowing eastward at 1.5 m/s. a) What is her velocity relative to the ground? b) Suppose she wants to arrive directly across from her starting point. In what direction must she head? What will be her...
  48. B

    How Does a Rowboat's Angle Affect Its Path Across a River with a Current?

    A rowboat crosses a river with a velocity of 3.30 mi/h at an angle of 62.5 degrees north of west relative to the water. The river is 0.505 mi wide and carries an eastward current of 1.25 mi/h. How far upstream is the boat when it reaches the opposite shore? Drew a staight line down in...
  49. A

    Alternate River crossing problem

    Hello, we are a few students that have been strugling with this question for some time now. We see no other solution than to ask you for help. Some clues would atleast help us on the way:) Here follows the question: Homework Statement A man wants to cross a river that is 500 meters wide...
  50. B

    Unique skull found by river, Anybody recognize?

    Unique skull found by river, Anybody recognize?? I live in western Ma and found this by the Connecticut river one day...I was wondering if anybody could tell me what it might be from
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