599
xkcd #2935: Ocean Loop (imgs.xkcd.com)
submitted 2 years ago by to c/xkcd@lemmy.world
23 comments fedilink hide all child comments
 

https://xkcd.com/2935

Alt text:

I can't believe they wouldn't even let me hold a vote among the passengers about whether to try the loop.

you are viewing a single comment's thread
view the rest of the comments
[–] 9 points 2 years ago (2 children)

Holy shit I wonder if it's even humanly possible to build one of these in the ocean for any size ship.

  • permalink
  • fedilink
  • source
  • hideshow 4 child comments
    •
  • [–] 7 points 2 years ago (2 children)

    Maybe something small, like a jetski…

  • permalink
  • fedilink
  • source
  • parent
  • hideshow 4 child comments
    •
  • [–] 5 points 2 years ago (1 child)

    Cruise ship or bust.

    And it's just a drawing but I'm trying to realize it in actual size. Cruise ships are huge, pushing 250 or so feet out of the water. That's considered a high-rise in the construction world.

    Now I look at that loopdy-lopp and say hey, that boat could fit. I'm ignoring all the other physics and shit and just Matchbox car'g that boat through that loop. That makes that loop like, what, 1000 feet? And that is ignoring the structure beneath the surface, and also the other dimensions of this, and the sheer velocity and volume of water.

    So I'm gonna call this one a hard maybe. Perhaps if the world could set aside it's differences, we could do a sort of space race, but instead a ship flip, or a boat float, or some other rhyme.

  • permalink
  • fedilink
  • source
  • parent
  • hideshow 2 child comments
    •
  • [–] 4 points 2 years ago (1 child)

    You just have to go fast enough. The minimum speed keeping you from falling out of a circular loop is sqrt(gr), with gravitational acceleration g and loop radius r. 10m radius requires 36km/h, which might be suitable for a Jetski. Larger ships need bigger loops to physically fit, and consequently larger speeds. It's quite surprising, but a monstrous 100m radius loop needs less than 120km/h.

  • permalink
  • fedilink
  • source
  • parent
  • hideshow 2 child comments
    •
  • [–] 1 point 2 years ago (1 child)

    so mass doesn't factor into the equation??? a Jetski made from aluminum would need the same speed as from osmium?

  • permalink
  • fedilink
  • source
  • parent
  • hideshow 2 child comments
    •
  • [–] 1 point 2 years ago

    I think so. At the apex of the loop gravity balances centrifugal force, Fg = Fc, when going the minimal speed necessary to get through the loop. Fg = m g, Fc = m v^2 / r. So mass m drops out of the equation.

  • permalink
  • fedilink
  • source
  • parent