11 min read

Source: Roblox Creator Hub · CC BY 4.0 · View source · Code samples: MIT Imported 2026-10-03. Formatting adapted for this site.

LinearVelocity

Inherits from: Constraint → Instance → Object

The LinearVelocity constraint applies force on an assembly to maintain a constant linear velocity. It can be set to apply force along a Vector3, line, or 2D plane. Alternatively:

If you want to control the amount of force applied, use a VectorForce constraint.
If you only need initial linear velocity, set the AssemblyLinearVelocity property directly on the assembly.

When configuring this constraint, it may be helpful to study Roblox Units to understand how Roblox units compare to metric units.

Relativity

Application of velocity can be controlled through the constraint's RelativeTo property. If set to World, force will be applied in world coordinates, independent of the parent or attachment orientations. If set to Attachment0 or Attachment1, force will be applied relative to Attachment0 or Attachment1 respectively.

Inherits from: Constraint

Memory category: BaseParts

Properties

Name	Type / Returns	Description
LinearVelocity.ForceLimitMode	ForceLimitMode	Determines how the constraint force will be limited.
LinearVelocity.ForceLimitsEnabled	boolean	Determines if the constraint force will be limited or if the physics solver can apply an unlimited force to achieve the target velocity.
LinearVelocity.LineDirection	Vector3	The normalized `Vector3` direction for constraining the velocity along a line.
LinearVelocity.LineVelocity	float	Float value of the velocity when `VelocityConstraintMode` is set to `Line`.
LinearVelocity.MaxAxesForce	Vector3	Maximum force along each axis that the constraint can apply to achieve the vector velocity. Only used if `ForceLimitsEnabled` is `true`, `ForceLimitMode` is `PerAxis`, and `VelocityConstraintMode` is `Vector`.
LinearVelocity.MaxForce	float	Maximum magnitude of the force vector the constraint can apply.
LinearVelocity.MaxPlanarAxesForce	Vector2	Maximum force along each axis that the constraint can apply to achieve the plane velocity. Only used if `ForceLimitsEnabled` is `true`, `ForceLimitMode` is `PerAxis`, and `VelocityConstraintMode` is `Plane`.
LinearVelocity.PlaneVelocity	Vector2	`Vector2` value of the velocity in each tangent direction of the plane.
LinearVelocity.PrimaryTangentAxis	Vector3	The primary axis in the plane, when `VelocityConstraintMode` is set to `Plane`.
LinearVelocity.ReactionForceEnabled	boolean	Determines whether an equal and opposite reaction force is also applied to the assembly of `Attachment1` when `RelativeTo` is `Attachment1`.
LinearVelocity.RelativeTo	ActuatorRelativeTo	Sets the `ActuatorRelativeTo` property for the constraint.
LinearVelocity.SecondaryTangentAxis	Vector3	The secondary axis in the plane, when `VelocityConstraintMode` is set to `Plane`.
LinearVelocity.VectorVelocity	Vector3	`Vector3` velocity value when `VelocityConstraintMode` is set to `Vector`.
LinearVelocity.VelocityConstraintMode	VelocityConstraintMode	The mode of the constraint.

Inherited from Constraint

Name	Type / Returns	Description
Constraint.Active	boolean	Indicates if the constraint is currently active in the world.
Constraint.Attachment0	Attachment	The `Attachment` that is connected to `Constraint.Attachment1`.
Constraint.Attachment1	Attachment	The `Attachment` that is connected to `Constraint.Attachment0`.
Constraint.Color	BrickColor	The color of the constraint.
Constraint.Enabled	boolean	Toggles whether or not the constraint is enabled.
Constraint.Visible	boolean	Toggles the constraint's visibility.

Inherited from Instance

Name	Type / Returns	Description
Instance.Archivable	boolean	Determines if an `Instance` and its descendants can be cloned using `Instance:Clone()`, and can be saved/published.
Instance.archivable	boolean
Instance.Capabilities	SecurityCapabilities	The set of capabilities allowed to be used for scripts inside this container.
Instance.IsInSandbox	boolean	Indicates whether the instance is inside a sandboxed container.
Instance.Name	string	A non-unique identifier of the `Instance`.
Instance.Parent	Instance	Determines the hierarchical parent of the `Instance`.
Instance.PredictionMode	PredictionMode	Reflects the client-side prediction mode applied to the instance under server-authoritative physics.
Instance.RobloxLocked	boolean	A deprecated property that used to protect `CoreGui` objects.
Instance.Sandboxed	boolean	When enabled, the instance can only access abilities in its `Capabilities` list.
Instance.UniqueId	UniqueId	A unique identifier for the instance.

Inherited from Object

Name	Type / Returns	Description
Object.ClassName	string	A read-only string representing the class this `Object` belongs to.
Object.className	string

LinearVelocity.ForceLimitMode

Determines how the constraint force will be limited. When set to Magnitude, the constraint force will have a magnitude less than MaxForce. When set to PerAxis, the force along each axis will be less than the corresponding value in MaxAxesForce when VelocityConstraintMode is Vector or the corresponding value in MaxPlanarAxesForce when VelocityConstraintMode is Plane. Only used when ForceLimitsEnabled is true.

Field	Value
type	ForceLimitMode
security	{"read":"None","write":"None"}
thread safety	ReadSafe
category	Limits
serialization	{"can_load":true,"can_save":true}
capabilities	["Physics"]
simulationAccess	true

LinearVelocity.ForceLimitsEnabled

Determines if the constraint force will be limited or if the physics solver can apply an unlimited force to achieve the target velocity. When enabled, the constraint force is limited based on ForceLimitMode. When disabled, the physics solver will always apply a force that is large enough to achieve the target velocity.

Field	Value
type	boolean
security	{"read":"None","write":"None"}
thread safety	ReadSafe
category	Mode
serialization	{"can_load":true,"can_save":true}
capabilities	["Physics"]
simulationAccess	true

LinearVelocity.LineDirection

The normalized Vector3 direction for constraining the velocity along a line, when VelocityConstraintMode is set to Line.

Field	Value
type	Vector3
security	{"read":"None","write":"None"}
thread safety	ReadSafe
category	Line
serialization	{"can_load":true,"can_save":true}
capabilities	["Physics"]
simulationAccess	true

LinearVelocity.LineVelocity

Float value of the velocity when VelocityConstraintMode is set to Line.

Field	Value
type	float
security	{"read":"None","write":"None"}
thread safety	ReadSafe
category	Line
serialization	{"can_load":true,"can_save":true}
capabilities	["Physics"]
simulationAccess	true

LinearVelocity.MaxAxesForce

Maximum force along each axis that the constraint can apply to achieve the target velocity. Only used if ForceLimitsEnabled is true, ForceLimitMode is PerAxis, and VelocityConstraintMode is Vector. The axes used to apply the limit correspond to the RelativeTo property.

Field	Value
type	Vector3
security	{"read":"None","write":"None"}
thread safety	ReadSafe
category	Limits
serialization	{"can_load":true,"can_save":true}
capabilities	["Physics"]
simulationAccess	true

LinearVelocity.MaxForce

Maximum magnitude of the force vector the constraint can apply. Only used if ForceLimitsEnabled is true and ForceLimitMode is Magnitude.

Field	Value
type	float
security	{"read":"None","write":"None"}
thread safety	ReadSafe
category	Limits
serialization	{"can_load":true,"can_save":true}
capabilities	["Physics"]
simulationAccess	true

LinearVelocity.MaxPlanarAxesForce

Maximum force along each axis that the constraint can apply to achieve the plane velocity. Only used if ForceLimitsEnabled is true, ForceLimitMode is PerAxis, and VelocityConstraintMode is Plane. The axes used to apply the limit correspond to the RelativeTo property.

Field	Value
type	Vector2
security	{"read":"None","write":"None"}
thread safety	ReadSafe
category	Limits
serialization	{"can_load":true,"can_save":true}
capabilities	["Physics"]
simulationAccess	true

LinearVelocity.PlaneVelocity

Vector2 value of the velocity in each tangent direction of the plane, when VelocityConstraintMode is set to Plane.

Field	Value
type	Vector2
security	{"read":"None","write":"None"}
thread safety	ReadSafe
category	Plane
serialization	{"can_load":true,"can_save":true}
capabilities	["Physics"]
simulationAccess	true

LinearVelocity.PrimaryTangentAxis

The primary axis in the plane, when VelocityConstraintMode is set to Plane. Value depends on the value of RelativeTo as follows:

If RelativeTo is set to Attachment0, this axis is the Axis of Attachment0.
If RelativeTo is set to Attachment1, this axis is the Axis of Attachment1.
If RelativeTo is set to World, this value must be specified in the world space.

Field	Value
type	Vector3
security	{"read":"None","write":"None"}
thread safety	ReadSafe
category	Plane
serialization	{"can_load":true,"can_save":true}
capabilities	["Physics"]
simulationAccess	true

LinearVelocity.ReactionForceEnabled

Determines whether the constraint applies an equal and opposite reaction force to the assembly of Attachment1. Defaults to true. This reaction force is relevant when RelativeTo is ActuatorRelativeTo.Attachment1 — the mode in which the constraint drives the Attachment0 assembly's velocity relative to the Attachment1 assembly. Because RelativeTo defaults to ActuatorRelativeTo.World, this property is typically only meaningful once RelativeTo is set to Attachment1.

When enabled in that mode, the constraint applies the reaction force to the Attachment1 assembly, coupling the two assemblies. When disabled, the constraint applies force only to the Attachment0 assembly; the Attachment1 assembly receives no reaction force, though its pose and velocity are still read as the reference frame for the target velocity.

Field	Value
type	boolean
security	{"read":"None","write":"None"}
thread safety	ReadSafe
category	Mode
serialization	{"can_load":true,"can_save":true}
capabilities	["Physics"]
simulationAccess	true

LinearVelocity.RelativeTo

Sets the ActuatorRelativeTo property for the constraint.

Field	Value
type	ActuatorRelativeTo
security	{"read":"None","write":"None"}
thread safety	ReadSafe
category	Mode
serialization	{"can_load":true,"can_save":true}
capabilities	["Physics"]
simulationAccess	true

LinearVelocity.SecondaryTangentAxis

The secondary axis in the plane, when VelocityConstraintMode is set to Plane. Value depends on the value of RelativeTo as follows:

If RelativeTo is set to Attachment0, this axis is the SecondaryAxis of Attachment0.
If RelativeTo is set to Attachment1, this axis is the SecondaryAxis of Attachment1.
If RelativeTo is set to World, this value must be specified in the world space.

Field	Value
type	Vector3
security	{"read":"None","write":"None"}
thread safety	ReadSafe
category	Plane
serialization	{"can_load":true,"can_save":true}
capabilities	["Physics"]
simulationAccess	true

LinearVelocity.VectorVelocity

Vector3 velocity value when VelocityConstraintMode is set to Vector.

Field	Value
type	Vector3
security	{"read":"None","write":"None"}
thread safety	ReadSafe
category	Vector
serialization	{"can_load":true,"can_save":true}
capabilities	["Physics"]
simulationAccess	true

LinearVelocity.VelocityConstraintMode

The mode of the constraint: Line, Plane, or Vector. Default is Vector.

Field	Value
type	VelocityConstraintMode
security	{"read":"None","write":"None"}
thread safety	ReadSafe
category	Mode
serialization	{"can_load":true,"can_save":true}
capabilities	["Physics"]
simulationAccess	true

Methods

Inherited from Constraint

Name	Type / Returns	Description
Constraint:GetDebugAppliedForce	Vector3
Constraint:GetDebugAppliedTorque	Vector3

Inherited from Instance

Name	Type / Returns	Description
Instance:AddTag	()	Applies a tag to the instance.
Instance:children	Instances	Returns an array of the object's children.
Instance:ClearAllChildren	()	This method destroys all of an instance's children.
Instance:Clone	Instance	Create a copy of an instance and all its descendants, ignoring instances that are not `Archivable`.
Instance:clone	Instance
Instance:Destroy	()	Sets the `Instance.Parent` property to `nil`, locks the `Instance.Parent` property, disconnects all connections, and calls `Destroy()` on all children.
Instance:destroy	()
Instance:FindFirstAncestor	Instance?	Returns the first ancestor of the `Instance` whose `Instance.Name` is equal to the given name.
Instance:FindFirstAncestorOfClass	Instance?	Returns the first ancestor of the `Instance` whose `Object.ClassName` is equal to the given className.
Instance:FindFirstAncestorWhichIsA	Instance?	Returns the first ancestor of the `Instance` for whom `Object:IsA()` returns true for the given className.
Instance:FindFirstChild	Instance?	Returns the first child of the `Instance` found with the given name.
Instance:findFirstChild	Instance
Instance:FindFirstChildOfClass	Instance?	Returns the first child of the `Instance` whose `ClassName` is equal to the given class name.
Instance:FindFirstChildWhichIsA	Instance?	Returns the first child of the `Instance` for whom `Object:IsA()` returns true for the given className.
Instance:FindFirstDescendant	Instance?	Returns the first descendant found with the given `Instance.Name`.
Instance:GetActor	Actor?	Returns the `Actor` associated with the Instance, if any.
Instance:GetAttribute	Variant	Returns the value which has been assigned to the given attribute name.
Instance:GetAttributeChangedSignal	RBXScriptSignal	Returns an event that fires when the given attribute changes.
Instance:GetAttributes	Dictionary	Returns a dictionary of the instance's attributes.
Instance:GetChildren	Instances	Returns an array containing all of the instance's children.
Instance:getChildren	Instances
Instance:GetDebugId	string	Returns a coded string of the debug ID used internally by Roblox.
Instance:GetDescendants	Instances	Returns an array containing all of the descendants of the instance.
Instance:GetFullName	string	Returns a string describing the instance's ancestry.
Instance:GetStyled	Variant	Returns the styled or explicitly modified value of the specified property, or else the default property value if it hasn't been styled/modified.
Instance:GetStyledPropertyChangedSignal	RBXScriptSignal	Returns an event that fires when the given style property changes on the instance.
Instance:GetTags	Array	Gets an array of all tags applied to the instance.
Instance:HasTag	boolean	Check whether the instance has a given tag.
Instance:IsAncestorOf	boolean	Returns true if an `Instance` is an ancestor of the given descendant.
Instance:IsDescendantOf	boolean	Returns `true` if an `Instance` is a descendant of the given ancestor.
Instance:isDescendantOf	boolean
Instance:IsPropertyModified	boolean	Returns `true` if the value stored in the specified property is not equal to the code-instantiated default.
Instance:QueryDescendants	Instances	Returns an array containing all descendants of the instance that match the `selector` string.
Instance:Remove	()	Sets the object's `Parent` to `nil`, and does the same for all its descendants.
Instance:remove	()
Instance:RemoveTag	()	Removes a tag from the instance.
Instance:ResetPropertyToDefault	()	Resets a property to its default value.
Instance:SetAttribute	()	Sets the attribute with the given name to the given value.
Instance:WaitForChild	Instance	Returns the child of the `Instance` with the given name. If the child does not exist, it will yield the current thread until it does.

Inherited from Object

Name	Type / Returns	Description
Object:GetPropertyChangedSignal	RBXScriptSignal	Get an event that fires when a given property of the object changes.
Object:IsA	boolean	Returns true if an object's class matches or inherits from a given class.
Object:isA	boolean

Events

Inherited from Instance

Name	Type / Returns	Description
Instance.AncestryChanged		Fires when the `Instance.Parent` property of this object or one of its ancestors is changed.
Instance.AttributeChanged		Fires whenever an attribute is changed on the `Instance`.
Instance.ChildAdded		Fires after an object is parented to this `Instance`.
Instance.childAdded
Instance.ChildRemoved		Fires after a child is removed from this `Instance`.
Instance.DescendantAdded		Fires after a descendant is added to the `Instance`.
Instance.DescendantRemoving		Fires immediately before a descendant of the `Instance` is removed.
Instance.Destroying		Fires immediately before (or is deferred until after) the instance is destroyed via `Instance:Destroy()`.
Instance.StyledPropertiesChanged		Fires whenever any style property is changed on the instance, including when a property is set to `nil`.

Inherited from Object

Name	Type / Returns	Description
Object.Changed		Fires immediately after a property of the object changes, with some limitations.