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How do I create centripetal force via a script?

Asked by

Br4veh3art23 46

7 years ago

I know the formula for centripetal force, however, I can't get it to work in Roblox. Here is my current code:

wait(0.5)

local RunService = game:GetService("RunService")

RunService.RenderStepped:connect(function()
    local Part = workspace.Part
    local Center = workspace.Center
    local m = Part:GetMass()
    local r = (Part.Position - Center.Position).magnitude
    local v = Vector3.new(math.sqrt(Part.Velocity.x), math.sqrt(Part.Velocity.y), math.sqrt(Part.Velocity.z))
    local mv = m * v
    local fc = (m * v/r)
    Part.Velocity = fc
end)

Whenever the script runs, it destroys the part (I assume that the velocity is carrying it below the destroy point) and I can't figure out how to fix it. Also, I'm waiting 0.5 seconds so that workspace.Part has enough time to drop someways and gain momentum. Also, here's a link to the Wikipedia page on centripetal force: https://en.wikipedia.org/wiki/Centripetal_force

Thanks in advance, Br4veh3art23

I don't think the Variable mv was ever used. thesit123 509 — 7y

I also don't think :GetMass() returns Vector3 values. thesit123 509 — 7y

Alright, I now have set m to be a Vector3 variable (All of the values are Part:GetMass()) and am now using mv, and changed it to Vector3.new(m * v), still not working. Br4veh3art23 46 — 7y

1 answer

Answered by

bigboy77584 19

7 years ago

You have a few problems with your script. Keep in mind the formula for centripetal force is mv^2/r and you are square rooting your velocity when it should actually be squared. Also, Velocity is a read-only value and the only way to actually apply forces and velocities to objects is to use body movers or CFrame. You can get the round about effect of what you want by doing this:

local edgePart = script.Parent
local radius = workspace.rad
local mass = edgePart:GetMass()

local RunService = game:GetService('RunService')

local tanVel = Instance.new('BodyVelocity', edgePart)
tanVel.Velocity = edgePart.CFrame.lookVector * 10

local cenForce = Instance.new('BodyForce', edgePart)

wait()
edgePart.Anchored = false

RunService.RenderStepped:connect(function()
    local v = tanVel.Velocity
    local r = edgePart.Position - radius.Position
    local direction = r.unit
    local radMag = r.magnitude
    cenForce.Force = (mass * (v.magnitude^2) / radMag) * direction
    tanVel.Velocity = 10 * cenForce.Force.unit:Cross(edgePart.CFrame.upVector)
end)

In this script, I create a body velocity that acts as the tangential velocity which always travels normal to the centripetal force. In order to accomplish this, you need to take take the cross product of the centripetal force and the other vector you want the tangential velocity to be normal to. In this case, I opted for the edge part's up facing direction in order to achieve a nice flat orbit. I hope this helps you out :)

On a side note, if you would be interested in accomplishing this with CFrame, I recommend reading up egomoose's guide on Hooke's law and inverse kinematics (http://wiki.roblox.com/index.php?title=Springs) in which he uses metatables to store velocity, acceleration and position vectors. I managed to use it to create a simulation of newtons law of gravitation (basically the same thing as this).

Okay, I found a different way of doing it using CFrame:toObjectSpace() https://scriptinghelpers.org/questions/45673/how-do-i-make-this-move-in-uniform-circular-motion how would I make this script move the part in uniform circular motion? Br4veh3art23 46 — 7y

How do I create centripetal force via a script?

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