A friend and I have been having an ongoing debate for years. We were at a pub on a wharf, watching shipping container ships and cruise ships come into dock, and he posed the question. With no wind, no waves, perfect conditions, could he move the ship at all?
In: Planetary Science
The ship will be in water thus it has to push the water away to move forward.
So it depends on how is the ship shaped like and how deep is it from the surface.
If it is magically just on the surface or is a hovercraft, then it will not need to push any water away thus it can be pushed easily under ideal conditions.
It is the initial movement that presents the biggest challenge. That is a lot of inertia to overcome. Once the vessel is moving then the fluid dynamics matter but not before.
Here is someone pulling 70 small boats at age 70 by swimming.
Here’s a weirder thought than that. If you do a free body diagram, the tension on the line that would be pulled to do this would actually deform the (elastic steel) ships hull though it would be an un-measurably small amount.
Yes, with some difficulty.
In ideal conditions, the only thing you’d have to overcome would be the inertia of the container, which can only multiplicatively reduce the acceleration you apply, not reduce it to zero.
Assuming you were somehow immune to being moved in turn by the equal and opposite reaction to what you’re exerting (perhaps you are rooted by footstraps or a mechanism similar to what locks boots into skis and snowboards), you would gradually be able to move it. The more massive the container, the slower the process would be.
> no wind, no waves, perfect conditions,
IOW, conditions that don’t exist anywhere. There’s always some movement in the air, even if you don’t feel it as wind on your skin. The slightest difference in air pressure on both sides of a ship, a difference that’s way too small for you to perceive as wind, will create a force that’s too strong for you to overcome.
Yes.
Source: I have done it, granted it was a Corvette sized ship but the principle remains
Here’s an answer that’ll blow your mind: in ideal conditions like you stated (no wind, waves, etc), you could move the ship without even touching it. All you have to do is stand near it, and the gravitational attraction between your body and the ship will pull it towards you.
The Newtonian laws are clear on it: the force you pull the ship with accelerates it proportionally to the rapport between your weight and the ship’s. If you weigh 85 kg and the cargo ship is a relatively small one weighing at around 100,000 tons, that means it outweighs you by a factor of 1.2 million, which means that any force you exert on it that would accelerate you forward by a certain value will accelerate the ship by a value that’s 1.2 million times smaller.
If the water was completely frictionless and there was no external force to impede your pulling (such as wind, water currents, waves etc.) then you could accelerate the ship to your walking speed with several days or weeks of nonstop pushing/pulling. In real life, even under the most favorable circumstances this would be impossible as even the resistance of the air and water themselves would undo most of the force you exert on the vessel.
Theoretically yes if you kept at it hard enough. Unlike moving something on land, you’re in luck in that something in fluid doesn’t have a static friction to overcome. If there was even the tiniest coefficient of static friction, you’d never be able to move it.
Also luckily, hydrodynamic drag goes with velocity, and you’re starting at 0 so drag is 0. Anything even moderately above zero will be more drag than any force you could apply. But you only said to move it, so almost no velocity, so almost no drag.
So you’re mainly dealing with f=ma.
Remember that Ford Lightning doing that huge feat pulling the million+ pounds of train cars? Between the low static friction and extremely low rolling resistance of steel wheels on steel rails, it didn’t really take much force to move it. A visual clue is that they used a standard tow strap to do it, nothing special. Really most decent electric cars could do this, and so could any gas or diesel if it had the right gearing.
If you were floating on the water next to the boat and push youself away wouldn’t the boat technically also have to move a tiny bit. (If you push yourself away from something the same weight of you, you and the object should both move the same distance, if it weighs twice as much it moves half the distance you do so a boat weighing no matter how much will always move a no matter how little distance right?)
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