5 ms·

This is a meaningless calculation. It's not as though the amount of energy required to move something a specific distance is weight related. The amount of for

This is a meaningless calculation. It's not as though the amount of energy required to move something a specific distance is weight related. The amount of force required to accelerate it to a specific velocity is, but once at that velocity, energy required is a function of friction. Of course larger objects have more air friction on average, but really what you want is some measure of the surface area of the object. Bah, not that it matters in the least.

ghshephard 16y ago
"It's not as though the amount of energy required to move something a specific distance is weight related. " " really what you want is some measure of the surface area of the object." http://en.wikipedia.org/wiki/Rolling_resistance http://en.wikipedia.org/wiki/Rolling_resistance
oiuyftgrghjk 16y ago
Interesting comparison. A container ship does about 24knots = 40feet/second It uses around 350tons of fuel/day = 4.5 l/s = 1.2USgall/s So it does a very similar consumption - around 35feet/gallon While carrying 150,000tons of cargo = 320million pounds.
- xxpor 16y ago
  The low speed (90 rpm) diesels in those ships are by far and away the most thermally efficient internal combustion engines on the planet. The biggest ones approach 50% efficient. http://en.wikipedia.org/wiki/W%C3%A4rtsil%C3%A4-Sulzer_RTA96-C http://en.wikipedia.org/wiki/W%C3%A4rtsil%C3%A4-Sulzer_RTA96...
  - tocomment 16y ago
    Why is that? Why don't they use these to generate electri ity?
    - oiuyftgrghjk 16y ago
      Because external combustion engines (boiler + turbine) are more efficient and cheaper to build at large scale
      - tocomment 16y ago
        So why not use those in ships?
        ramchip 16y ago
        According to this marine engineering book ( http://books.google.com/books?id=PCSpWWuTgkkC&lpg=PA53&pg=PA53#v=onepage&q&f=false http://books.google.com/books?id=PCSpWWuTgkkC&lpg=PA53&#... ) and this website ( http://library.fentu.ru/book/gumi/101/English/section_1_main_marine_engines.html http://library.fentu.ru/book/gumi/101/English/section_1_main... ) which seems based on the book, slow diesel engines are more efficient, but turbines are used in ships. The steam turbine has until recently been the first choice for very large power main propulsion units. Its advantages of little or no vibration, low weight, minimum space requirements and low maintenance costs are considerable. In steam turbines high pressure steam is directed into a series of blades or vanes attached to a shaft, causing it to rotate. This rotary motion is transferred to the propeller shaft by gears. Steam is produced by boiling water in a boiler, which is fired by oil. Recent developments in steam turbines which have reduced fuel consumption and raised power output have made them more attractive as an alternative to diesel power in ships. They are 50 per cent lighter and on very large tankers some of the steam can be used to drive the large cargo oil pumps. Turbines are often used in container ships, which travel at high speeds.
    - ramchip 16y ago
      The slow diesel engine can be connected directly to the propeller shaft, making it mechanically very efficient. I could be wrong, but I don't think a 90 RPM engine with extremely high torque would be appropriate for hooking directly to an alternator.

ghshephard 16y ago

"It's not as though the amount of energy required to move something a specific distance is weight related. " " really what you want is some measure of the surface area of the object." http://en.wikipedia.org/wiki/Rolling_resistance http://en.wikipedia.org/wiki/Rolling_resistance

oiuyftgrghjk 16y ago

Interesting comparison. A container ship does about 24knots = 40feet/second It uses around 350tons of fuel/day = 4.5 l/s = 1.2USgall/s So it does a very similar consumption - around 35feet/gallon While carrying 150,000tons of cargo = 320million pounds.

xxpor 16y ago
The low speed (90 rpm) diesels in those ships are by far and away the most thermally efficient internal combustion engines on the planet. The biggest ones approach 50% efficient. http://en.wikipedia.org/wiki/W%C3%A4rtsil%C3%A4-Sulzer_RTA96-C http://en.wikipedia.org/wiki/W%C3%A4rtsil%C3%A4-Sulzer_RTA96...
- tocomment 16y ago
  Why is that? Why don't they use these to generate electri ity?
  - oiuyftgrghjk 16y ago
    Because external combustion engines (boiler + turbine) are more efficient and cheaper to build at large scale
    - tocomment 16y ago
      So why not use those in ships?
      - ramchip 16y ago
        According to this marine engineering book ( http://books.google.com/books?id=PCSpWWuTgkkC&lpg=PA53&pg=PA53#v=onepage&q&f=false http://books.google.com/books?id=PCSpWWuTgkkC&lpg=PA53&#... ) and this website ( http://library.fentu.ru/book/gumi/101/English/section_1_main_marine_engines.html http://library.fentu.ru/book/gumi/101/English/section_1_main... ) which seems based on the book, slow diesel engines are more efficient, but turbines are used in ships. The steam turbine has until recently been the first choice for very large power main propulsion units. Its advantages of little or no vibration, low weight, minimum space requirements and low maintenance costs are considerable. In steam turbines high pressure steam is directed into a series of blades or vanes attached to a shaft, causing it to rotate. This rotary motion is transferred to the propeller shaft by gears. Steam is produced by boiling water in a boiler, which is fired by oil. Recent developments in steam turbines which have reduced fuel consumption and raised power output have made them more attractive as an alternative to diesel power in ships. They are 50 per cent lighter and on very large tankers some of the steam can be used to drive the large cargo oil pumps. Turbines are often used in container ships, which travel at high speeds.
  - ramchip 16y ago
    The slow diesel engine can be connected directly to the propeller shaft, making it mechanically very efficient. I could be wrong, but I don't think a 90 RPM engine with extremely high torque would be appropriate for hooking directly to an alternator.