What are some civilian or industrial applications of a large amount of linear force. I.e. if a magical symbol was inscribed on a piece of paper the next physical object that touches the symbol would have forced applied to that object from that direction. I originally thought of this idea as a way to make magical breach loading cannons (the hinge swings shut and the cannonball is forced forward, no need for reinforced butts as all the force is directed in one direction). The other application I could think of was landmines (the symbol is left on the ground and someone steps on it and is flung in the air or has their legs crumple).

Early industrial uses of power all seem to be rotational, ie spinning wheel grinds grain, spinning wheel turns textile mills, spinning wheel makes car move. And although there are gears that transfer linear power into rotational power, they don't seem to have the durability/ usage? for explosive levels of force.

As a constrain, the magical symbols require a non-negligible amount of effort to create but can be scaled more forceful or less forceful withe more force taking more effort. Tech level can vary anywhere between Roman era tech to early modern period.

Thanks :)

edit: forgot to specify how long the force is applied, it is applied instantly or very near instantly, and then the magical symbols disappear.

edit 2: to add a clarifying point, the force/ energy from the magic comes from the energy created/ generated in a fire in joules or something. Bigger fire -> more energy but more effort, smaller fire -> less energy. Think of it as like a transfer of energy from heat/ light to direction. Therefore for small things like a winepress or whatnot, it would probably not be efficient to create a fire and a magical spell just to do something you can very easily do with muscle power, but for a cannon, you have the ability to store huge amounts of energy and use it at once to fire a cannon ball.

Bottom line, the question boils down to: "I have a magic spell that can impart to the target a certain amount of kinetic energy, putting it in a strict linear motion, in a sudden (instantaneous) way. How could someone harvest this energy for industrial purposes?"

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    $\begingroup$ You failed to specify for how long the force is applied on the target. If it's "forever", this magic can only be used for destructive purposes (eliminate the target from the world accelerating it forever in the skies or pin them forever against an obstacle that can resist the force). $\endgroup$ Commented Nov 30, 2021 at 1:56
  • $\begingroup$ Hey, I asked for how long it lasts not how fast is applied! $\endgroup$ Commented Nov 30, 2021 at 2:01
  • $\begingroup$ Over what distance is the force applied? e.g. if I'm across the room from a symbol pointed my way, does it hit me? Across the street? Across a football field? $\endgroup$
    – Cadence
    Commented Nov 30, 2021 at 2:04
  • $\begingroup$ Physical connection of a physical object (not air) is required. So it means it could not be used in a dusty/ sandy environment or dust shrapnel would be sprayed everywhere if a a lot of dust/ sand lands of the symbol after its completed I'd imagine (not the best a physics). Also still doing research to how force is applied to liquids and its resulting impact so I don't know that. $\endgroup$
    – yeet1000
    Commented Nov 30, 2021 at 2:06
  • $\begingroup$ "explosive levels of force" - can this force be dampened? For example, if we apply this magic to a bag of sand, would the entire bag accelerate, or only the the grains directly contacting the magical sheet of paper would? $\endgroup$
    – Alexander
    Commented Nov 30, 2021 at 2:07

2 Answers 2


Too many to enumerate. A small sampling:

  • $\begingroup$ Single time use or what? Because if the spell last forever, you only have the equivalent of a constant gravity acting in the direction of the force forever. Not very useful if you need to spend extra effort to restore the initial conditions. $\endgroup$ Commented Nov 30, 2021 at 2:00
  • $\begingroup$ @AdrianColomitchi If the application of force lasted forever, applying the spell to an object and throwing it into the air to would accelerate it to arbitrarily close to light speed over sufficient time, requiring the spell to provide effectively infinite energy. Presumably that is not what the querent intended. $\endgroup$ Commented Nov 30, 2021 at 2:05
  • $\begingroup$ I don't know what s/he intended. By the gits of her/his question (explosive force), I think he's confused between applying a force (and get mechanical work in return) and collision (momentum/energy exchange in a very short time). If it is the latter, then his question doesn't provide enough details about the energy available in the "explosive spell". $\endgroup$ Commented Nov 30, 2021 at 2:16
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    $\begingroup$ Then using the "force" to describe what is happening is improper and doesn't make sense. For example, if you apply a force of 10N over 10 picoseconds, you don't have much in return. The question should be described in terms of energy that is imparted on the target in such a way that is causing it to move linearly. $\endgroup$ Commented Nov 30, 2021 at 2:34
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    $\begingroup$ @yeet1000 The technical term that you are looking for to describe "a big shove" is en.wikipedia.org/wiki/Impulse_(physics), in the second sense of "a fast-acting force" as mentioned about halfway down the page. $\endgroup$ Commented Nov 30, 2021 at 2:35

Assuming that the symbol doesn't wear out, what you've got is a perpetual motion machine. A piston, a spring, the piece of paper, and a cam, and you've got a steam engine without the steam.

You dismiss the use of "explosive levels of force", but explosions or extraordinary pressure is how internal combustion engines and steam engines work. If the symbol wears out after one use, then a mechanism to replace each sheet with a new one would be trickier to engineer, and you'd effectively be exchanging one fuel for another (a stack of runes as opposed to a tank of gas), but transforming explosive energy into rotational energy is something that's been around for quite a long time.


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