Force

[Vzearr]

Different types of force:​

Force isn't just 1 type of force, in fiction, we usually just utilise the formula F = M * A. However, some feats don't fall under this formula.

Force = Mass * Acceleration
Centripetal Force = mass*velocity^2/radius
What is Centripetal force? A centripetal force is a force that makes a body follow a curved path.

Buoyant Force = fluid density * acceleration due to gravity * Fluid volume
What is Buoyant force? Buoyancy, or upthrust is a net upward force exerted by a fluid that opposes the weight of a partially or fully immersed object.

Gravitational Force = (Gravitational constant * mass of body 1 * mass of body 2) / distance between the 2 bodies^2
What is gravitational force? The force that pulls objects with mass toward each other.

Frictional Force = coefficient of friction * normal force
What is Frictional force? Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other.

These are the forces I believe apply most to fictional feats. I want to add these to the calculations page, just need approval.​

 

[Vzearr]

Tagging calc group members (I'm not sorry anymore): @DontTalkDT @Executor_N0 @Therefir @Ugarik @DMUA @Damage3245 @TheRustyOne @DemonGodMitchAubin @Jasonsith @Wokistan @Armorchompy @Migue79 @Psychomaster35 @Dark-Carioca @AbaddonTheDisappointment @Aguywhodoesthings @Agnaa @Dalesean027 @DemiiPowa @SeijiSetto @SunDaGamer @Mr. Bambu

 

[Agnaa]

We already use most of these, they just don't come up too much.

We don't really use frictional force since the coefficient of friction is often hard to find, and all it does is make feats higher if you can find that coefficient. Which is a bit weird, since it relatively nerfs some feats based on kinda arbitrary conditions, and it's something that often is seemingly missing in works.

 

[Vzearr]

We already use most of these, they just don't come up too much.

I know, I just want them on the page with examples of each one so new users know what to use for their feats.

 

[Agnaa]

I worry about information overload & bloat for things that don't come up very often. So I'm leaning against this suggestion.

If you're going to also include examples, I'd like you to type those up so I'd know what I'd be accepting/rejecting.

 

[Vzearr]

Force = Mass * Acceleration​

Character A throws Character B in a straight line.

Centripetal Force = mass*velocity^2*radius
What is Centripetal force? A centripetal force is a force that makes a body follow a curved path.​

Character A swings Character B in a circle.

Buoyant Force = fluid density * acceleration due to gravity * Fluid volume
What is Buoyant force? Buoyancy, or upthrust is a net upward force exerted by a fluid that opposes the weight of a partially or fully immersed object.​

Character A lifts Character B up from water.

Gravitational Force = (Gravitational constant * mass of body 1 * mass of body 2) / distance between the 2 bodies^2
What is gravitational force? The force that pulls objects with mass toward each other.​

Character A drops a meteor, and it falls toward the ground due to Earth's gravity.

Frictional Force = coefficient of friction * normal force
What is Frictional force? Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other.​

Character A pushes a boulder across cement.

 

[Agnaa]

Oh, just that brief huh? Meh, I'll vote neutral. Assuming the following issues are fixed:

• Buoyant Force stuff seems intuitively incomplete/misleading. My intuition tells me that buoyancy force is relevant in those sorts of cases, insofar as it offsets acceleration due to gravity. And that overall, it is important to know the volume of the object that is displacing the fluid (although this may have been what you meant by "fluid volume"), as well as the mass of the object (although this may be mostly relevant to know how exactly the buoyancy force, applied to that mass, offsets the acceleration gravitational force would provide).
• A meteor seems like a sub-optimal example for gravitational force. In those cases we'd usually just simplify down to 9.81 m/s^2 * mass of meteor. And, the force applied by that isn't really relevant to any character. Maybe swap out for something like a character pushing a planet to stop it from falling into a black hole.
• I don't know whether we actually use friction for cases like that, or if we just use normal force. Plus, this may deserve more work put into the example, since someone may pull out the wrong coefficient of friction for this sort of case (i.e. they may see that it's a boulder, and use the coefficient of friction for a sphere, despite that being relevant for air resistance, not for a sliding feat like this). Also, since cases like that would want the total force, it might be worth mentioning that you'd more want something like (1 + coefficient of friction) * normal force.

EDIT: I'd also point out another issue with doing frictional force that way; we don't know what the displacement would've been in a world without friction, so I don't think your derivation works. Hell, looking at it that way, I think we'd intuitively be taking into account frictional force for most calculations anyway; all that's happening is that we don't also derive the raw numbers that would apply if they were in an environment without friction (say, what their acceleration would be if they did the same feat in a vacuum).

 

[DMUA]

I don't know whether we actually use friction for cases like that, or if we just use normal force.

We have, in cases where it's specifically pushing something across a surface

It only nerfs it by like half on average, but it's pretty easy to apply

 

[Agnaa]

We have, in cases where it's specifically pushing something across a surface

It only nerfs it by like half on average, but it's pretty easy to apply

I don't know why we'd nerf it. They are still exerting that force, it's just that some of it gets wasted in friction, instead of in moving that object. It'd only nerf the acceleration of the object, if that was needed for another calc.

Only place where I can see that nerfing things, would be when a character's trying to stop an object's movement by pushing against it, as friction would be helping them slow it down. Which ig is fair, but does open the can of worms of using friction in other instances.

 

[DMUA]

I don't know why we'd nerf it. They are still exerting that force, it's just that some of it gets wasted in friction, instead of in moving that object.

It's just easier to push something across the ground instead of lift it entirely, even if not very much on high friction surfaces

 

[Agnaa]

It's just easier to push something across the ground instead of lift it entirely, even if not very much on high friction surfaces

It's not. You're just not often accelerating things at 9.81 m/s^2 across the ground.

Friction does not make it easier to move objects, it makes it harder. That's why many mechanical devices try to reduce friction. It's why much of waste heat occurs; the energy that would be going into moving something goes into heating it up instead. Air resistance is a kind of friction that occurs because there's a wall of particles objects hit when moving, that they need to move to continue moving, which doesn't occur in a vacuum.

 

[SeijiSetto]

Force = Mass * Acceleration
Centripetal Force = mass*velocity^2*radius​

centripetal is (mv^2)/r

 

[Executor_N0]

As said before, any method that can be used to find a force and it is at least usable under the context for practical reasons (Like how we accept calculations that are only approximations if they are overall under the same order of magnitude as the true value). If adding them to calc pages to make other calc members aware of that, it's perfectly fine as they are being used and are already accepted, so it would only need a text update.

 

[ElajRuengies]

It's not. You're just not often accelerating things at 9.81 m/s^2 across the ground.

Friction does not make it easier to move objects, it makes it harder. That's why many mechanical devices try to reduce friction. It's why much of waste heat occurs; the energy that would be going into moving something goes into heating it up instead. Air resistance is a kind of friction that occurs because there's a wall of particles objects hit when moving, that they need to move to continue moving, which doesn't occur in a vacuum.

So, every time I've pushed a box horizontally because it was just too heavy to pick up, I was actually having hysterical strength?

Never before have I seen a Calc Group Member be so confidently wrong about something. The literal definition of the coefficient of friction is-

Coefficient of friction (COF) is a dimensionless number that is defined as the ratio between friction force and normal force (Eqn (2.1))

The normal force is the force exerted on the object from ground that opposes the weight of the object due to gravity, and thus it's equal to the object's weight (unless there's something extra pushing it into the ground like a hydraulic press)

In other words, if the Coefficient of Friction between two surfaces is less than 1 (as it is for most substances), then the frictional force is less than the force of its weight. This means that pushing the object across the ground takes less force to overcome its friction than pulling it upward against gravity does.

Also, unless your pushing something across the ground crazy fast, or that object is very wide compared to its weight like a sail, then Air Resistance will be negligible.

Anywho, Coefficient of Friction comes in two flavors- static and dynamic. Static CoF is the force needed to get an object from stationary to moving, while Dynamic is the frictional force on an object that's already moving. Usually we only care about Static CoF since we don't care how fast a object is being pushed for Lifting Strength.

Obviously pushing an object horizontally can require more force than just picking it up if it's being accelerated by the pusher fast enough, but that force is thanks to how rapidly the pusher is moving, not because of friction.

And while having any CoF bigger than zero will add to the force required to move an object, that doesn't mean the resulting force will be bigger than the force required to lift the object off the ground. It's usually smaller.

 

[Agnaa]

So, every time I've pushed a box horizontally because it was just too heavy to pick up, I was actually having hysterical strength?

Were you pushing those boxes across the ground at 9.81 m/s^2?

Never before have I seen a Calc Group Member be so confidently wrong about something. The literal definition of the coefficient of friction is-

The normal force is the force exerted on the object from ground that opposes the weight of the object due to gravity, and thus it's equal to the object's weight (unless there's something extra pushing it into the ground like a hydraulic press)

In other words, if the Coefficient of Friction between two surfaces is less than 1 (as it is for most substances), then the frictional force is less than the force of its weight. This means that pushing the object across the ground takes less force to overcome its friction than pulling it upward against gravity does.

Yes, there is usually less of an opposing force provided by friction, than there is applied by gravity.

However

When you're moving an object, you're not just matching the opposing force, you're also providing force to move the object. Displacing it, providing it with acceleration.

I think it may have been wrong for me to say that it adds to the normal force. Rather, it adds to the force required to accelerate the object in that direction.

Moving an object along a surface is more difficult than moving it in the vacuum of space. Friction reduces the amount of force applied which goes to accelerating the object you're trying to move. Friction does not give you free energy out of nowhere.

Also, unless your pushing something across the ground crazy fast, or that object is very wide compared to its weight like a sail, then Air Resistance will be negligible.

It's negligible, but it exists.

 

[Floxy178]

So, every time I've pushed a box horizontally because it was just too heavy to pick up, I was actually having hysterical strength?

Never before have I seen a Calc Group Member be so confidently wrong about something. The literal definition of the coefficient of friction is-

The normal force is the force exerted on the object from ground that opposes the weight of the object due to gravity, and thus it's equal to the object's weight (unless there's something extra pushing it into the ground like a hydraulic press)

In other words, if the Coefficient of Friction between two surfaces is less than 1 (as it is for most substances), then the frictional force is less than the force of its weight. This means that pushing the object across the ground takes less force to overcome its friction than pulling it upward against gravity does.

Also, unless your pushing something across the ground crazy fast, or that object is very wide compared to its weight like a sail, then Air Resistance will be negligible.

Anywho, Coefficient of Friction comes in two flavors- static and dynamic. Static CoF is the force needed to get an object from stationary to moving, while Dynamic is the frictional force on an object that's already moving. Usually we only care about Static CoF since we don't care how fast a object is being pushed for Lifting Strength.

Obviously pushing an object horizontally can require more force than just picking it up if it's being accelerated by the pusher fast enough, but that force is thanks to how rapidly the pusher is moving, not because of friction.

And while having any CoF bigger than zero will add to the force required to move an object, that doesn't mean the resulting force will be bigger than the force required to lift the object off the ground. It's usually smaller.

I believe it's existance of gravity that misleads you, just compare pushing on ground considering friction and pushing while not considering it and you'll see the difference. Considering friction will require more initial force as Agnaa said.

 

[ElajRuengies]

I believe it's existance of gravity that misleads you, just compare pushing on ground considering friction and pushing while not considering it and you'll see the difference. Considering friction will require more initial force as Agnaa said.

Considering friction just means that it requires more force than none. In the context of what Agnaa was saying-

We have, in cases where it's specifically pushing something across a surface

It only nerfs it by like half on average, but it's pretty easy to apply

I don't know why we'd nerf it. They are still exerting that force, it's just that some of it gets wasted in friction, instead of in moving that object. It'd only nerf the acceleration of the object, if that was needed for another calc.

It's just easier to push something across the ground instead of lift it entirely, even if not very much on high friction surfaces

It's not. You're just not often accelerating things at 9.81 m/s^2 across the ground.

-that it required the same amount of force to push an object across the ground than it did to pick an object up, that's just wrong.

Also, CoF takes gravity into account. It's a ratio with respect to Normal Force; if gravity is zero then there's nothing actually pressing the object and the surfaces textures together, meaning frictional force is also gonna be zero.

 

[IDK3465]

Considering friction just means that it requires more force than none. In the context of what Agnaa was saying-




-that it required the same amount of force to push an object across the ground than it did to pick an object up, that's just wrong.

Also, CoF takes gravity into account. It's a ratio with respect to Normal Force; if gravity is zero then there's nothing actually pressing the object and the surfaces textures together, meaning frictional force is also gonna be zero.

I think there’s some confusion here regarding what exact mechanics are at play.
Dry friction is divided into two main types, with their own kinds of use cases: static and kinetic.

Static friction is essentially the force keeping a stationary object from moving across the ground. It’s this force that is the minimum you need to overcome to GET something to move. The formula to find this is simply N * μs. In this case, it would typically be less than the normal force (which, for all intents and purposes, is the force due to gravity). This is what Elaj is talking about when referring to friction.

Kinetic friction on the other hand is the force affecting an object already in motion, slowing it down over time. This is the force you need to constantly overcome in order to KEEP something moving. Unlike static, which is just frictional, the total force to accelerate an object accounting for friction is the kinetic frictional force (N * μk, the minimum to keep it going) plus the needed force (ma, the actual acceleration it’s physically going at). In this case, it can potentially be greater than the normal force, depending on the acceleration it’s going at. This is what Agnaa is talking about regarding friction.

 

[Floxy178]

Also, CoF takes gravity into account

Yeah, of course does.

It's a ratio with respect to Normal Force; if gravity is zero then there's nothing actually pressing the object and the surfaces textures together, meaning frictional force is also gonna be zero.

Ehm, I didn't say you should ignore existance of gravity? My point is that using "lifting" option misleads you due to existance of gravity as you should compare minimal force for lifting up smth with pushing it on ground at 9.81 m/s2, otherwise there'd be no point on comparision at all.

That's why just comparing 2 cases where friction is considered and not, is more clear and you'd see that consideration of it requires initial force to be higher.

-that it required the same amount of force to push an object across the ground than it did to pick an object up, that's just wrong.

No? Where exactly he claims that?