Go upstreem using the current?

[NathanS]

Is it possable to create a machine that would use the flow of a river to trasport itself upstreem? I was thinking you could gear down a waterwheel and connect it up to 4 wheels. But if then the machine should go faster and faster upsteem.

 

[Brie]

I would say no. You have to remember that the machine would be traveling in the opposite direction of the current. If you look at it this way if the machine is lets say "pushed" to get it started. The velocity of the car would counteract the velocity of the current. So from each blades standpoint, the current would be at a standstill and the blades would not "turn". Going back to the car, if the blades are not turning then the machine cant move.

The machine would work if the enegry from the water could be transfered to the car in a way that the car is not connected to the wheel/water...This is like standing on a boat and using a large fan to fill a sail to move the boat...the boat wouldnt move because the fan and sail are connected and their forces cancel each other out.

 

[AEB]

whereas the theory in this question is interesting the main problem is drag of teh stream, lets imagine for a moment that the river can power some thing that drives the unit faster up stream. the drag would increase so the energy the river is pushing on the unit would be the same the unit could use from the river. so at best you might be able to make a flotable anchor

 

[rgwalt]

Nope, it would violate the first law.

R

 

[spidey07]

Could you use some sort of undewater sail/wing and "tack" upstream? Sailboats do it all the time.

Air=fluid
Water=fluid

Seems like the principles would be the same, but the drag of the water might be too much?

 

[sgtroyer]

It seems attractive, but the problem is the keel. A sailboat has a keel that keeps it from slipping sideways in the water: it can only travel forward. So a sailboat can travel at an angle to the wind because of the force on the sail, and the force (in a different direction) of the water on the keel.

If your sail and your keel are both in the water, the same current will push on both, and it won't work.

It seems all of the problems stem from the boat being in the current. If the boat could put down anchor to stay stationary for awhile, charge up some batteries, and then motor upstream, it would work fine. Without some stationary attachment, though (an anchor, a rope to shore, etc), I just don't see a way to make it work.

 

[FrankSchwab]

sgtroyer hit it on the head. The Sailboat (or Iceboat, ...) use differences in velocity to generate an "upstream" motion. An iceboat uses it's blades on the ice to counteract and redirect the force on it's sail from the wind, much like the sailboat uses it's keel. Imagine a sailboat in the middle of the Pacific Ocean, with a 10 knot wind blowing out of the east and a 10 knot current flowing from the east. There's plenty of motion there, but the sailboat isn't going to go anywhere - there is no differential to exploit. I can, however, imagine a boat with a wheel that rides on the bottom of the river being able to go upstream, using the velocity differential between the streambed and the water to tack upstream like a sailboat or iceboat.

If the suggested mechanism of waterwheels was possible, imagine the other possibilities! An airplane with no motor, towed to speed then using the energy of the wind going past to power a means of propulsion to keep it up! An automobile towed to speed then using the energy of the wind going past as well as the speed of the roadway going past to power it forward!

/frank

 

[sgtroyer]

Good analogy. Never thought of it that way.

EDIT: What is it about trying to get something for nothing? Look at the threads posted lately. Boats going upstream for free, perpetual motion machines, easy algorithms for factoring large numbers... What's next?

 

[f95toli]

Originally posted by: sgtroyer
Good analogy. Never thought of it that way. EDIT: What is it about trying to get something for nothing? Look at the threads posted lately. Boats going upstream for free, perpetual motion machines, easy algorithms for factoring large numbers... What's next?

People are lazy

 

[Rainsford]

Originally posted by: sgtroyer
Good analogy. Never thought of it that way.

EDIT: What is it about trying to get something for nothing? Look at the threads posted lately. Boats going upstream for free, perpetual motion machines, easy algorithms for factoring large numbers... What's next?

That's what science is all about, finding easier ways to do things. Why do you think most stuff was invented? Because someone was lazy and wanted an easier way to do something. And as far as something for nothing, it's all about exploting physics to turn something you don't want into something you want. Look at the atomic bomb. Because of E=MC^2, you can give up a little mass to gain a lot of energy. In this particular case, the mass itself is relativly worthless by itself, but when it is converted into energy it becomes very important. Just my $0.02