What surface requires the least energy to travel over, land or water?

Question

What surface requires the least amount of energy to travel over.. land or water? Same weight.. flat land versus plat water..

It seems like it would be water.. like it's a no-brainer.. but I have seen some things* that make me wonder.. it seems like there might be more drag from the water surface contacting the boat hull. does anyone have any definitive proof?

* I saw an episode of Mythbusters where they tried to make a boat powered by compressed air.. it was a huge failure.

Answer 1

I suppose that depends on the object that's doing the travelling, and the rate of speed.

Water is a level surface and will evenly support a buoyant load. Land vehicles are supported on wheels and axles, and have a combination of road friction (rubber-to-road, tire pressure, etc) and mechanical friction (shocks, bearings, frame, etc). Bulk cargo transport, which strives for cost-efficiency, demonstrates that big ships are more efficient than trains which are more efficient than transport trucks. They wouldn't have dug canals across England during the industrial revolution if they wasn't efficiency in them.

However, friction becomes more significant at higher speeds -- friction through a medium operates as the cube of velocity. Water friction is, I believe, 112 times greater than air friction. So although a boat is only partially submerged, there will come a point as velocity goes up where the friction of the medium favours land travel. (side note: that's why hydrofoils are more efficient at high velocity than regular boats; they lift the boat out of the water to trade water friction for air friction.)

But the question was which surface took less energy to travel "over", which suggests traveling above the surface. Trick question - that means you'd have to be flying. So I'll answer neither.

(P.S.: WWII-era torpedoes used compressed air; they worked OK.)

Answer 2

Travel by rail requires a lot of energy to get started, but there is remarkable little energy required to maintain velocity.

And as you say, travel by water can involve a lot of resistance by the water on the hull.

I don't know what the actual numbers are and it is likely an exceedingly complex question for this forum.

Typically, you need to consider passenger miles per a certain quantity of fuel or energy cost. Right now, airplanes are comparable to automobiles in this respect.

Answer 3

Right off the bat, a propeller is going to accelerate still water in the opposite direction when it pushes you forward, something that doesn't happen to solid road when your wheels push against it, so this is loss right there. And hull friction, like you mention, as it moves water forward with you is a loss that land propulsion doesn't have. Definitely, hard round tires on a solid smooth road is ideal for propulsive efficiency.

Subjectively, I can tell you from experience that a 60-horsepower motorcycle greatly outperforms a 215-horsepower jet ski...

Answer 4

See I would have to say that it would be land, cause water does cause a huge drag on something. Think of it this way, running on land compared to running in water. I'm sure you have done both as we all have. If you haven't try it, then go try it. Its obviously harder in the water cause of the water holding you back. That's my thinking on it anyway. Hope I helped

Answer 5

in case you return and forth on land and crash you get terminal street rash,in case you crash on the water,you drown,in case you crash interior the air ,you get the better of the two worlds,scattered in little products over land or sea,so i prefer to not return and forth until i can take somebody deserving with me.