--- name: LineForce last_updated: 2026-06-11T23:11:57Z inherits: - Constraint - Instance - Object type: class memory_category: BaseParts summary: "Applies a force along the theoretical line connecting its two Attachments." --- # Class: LineForce > Applies a force along the theoretical line connecting its two > [Attachments](/docs/reference/engine/classes/Attachment.md). ## Description The `LineForce` constraint applies a force along the theoretical line connecting its two [Attachments](/docs/reference/engine/classes/Attachment.md). As the end points (attachments) move, the direction of force will change accordingly. When configuring this constraint, it may be helpful to study [Roblox Units](/docs/en-us/physics/units.md) to understand how Roblox units compare to metric units. #### Force Location By default, force is applied to either parent at its attachment location. If desired, force can be focused at each parent's center of mass by enabling [ApplyAtCenterOfMass](/docs/reference/engine/classes/LineForce.md). #### Inverse Square Law When [InverseSquareLaw](/docs/reference/engine/classes/LineForce.md) is `true`, the force magnitude is multiplied by the inverse square of the distance, meaning the force will increase exponentially as the two attachments get closer together, like magnets. When using this setting, it's recommended that you set a [MaxForce](/docs/reference/engine/classes/LineForce.md) threshold to prevent infinite force if the attachments align precisely. #### Reactionary Force By default, the constraint only applies force to [Attachment0](/docs/reference/engine/classes/Constraint.md), while [Attachment1](/docs/reference/engine/classes/Constraint.md) remains unaffected. However, force can be applied to both attachments in **equal and opposite directions** by enabling [ReactionForceEnabled](/docs/reference/engine/classes/LineForce.md). ## Properties ### Property: LineForce.ApplyAtCenterOfMass ```json { "type": "boolean", "access": "ReadWrite", "security": { "read": "None", "write": "None" }, "serialization": { "can_load": true, "can_save": true }, "thread_safety": "ReadSafe", "category": "LineForce", "capabilities": [ "Physics" ], "simulationAccess": true } ``` When `true`, force is applied at the center of mass of the parent assembly of [Attachment0](/docs/reference/engine/classes/LineForce.md), and the line determining the direction of the force will start at the said center of mass. When `false`, force is applied at [Attachment0](/docs/reference/engine/classes/LineForce.md) and the line determining the direction will also start at [Attachment0](/docs/reference/engine/classes/LineForce.md). ### Property: LineForce.InverseSquareLaw ```json { "type": "boolean", "access": "ReadWrite", "security": { "read": "None", "write": "None" }, "serialization": { "can_load": true, "can_save": true }, "thread_safety": "ReadSafe", "category": "LineForce", "capabilities": [ "Physics" ], "simulationAccess": true } ``` When `true`, the force magnitude is multiplied by the inverse square of the distance. ### Property: LineForce.Magnitude ```json { "type": "float", "access": "ReadWrite", "security": { "read": "None", "write": "None" }, "serialization": { "can_load": true, "can_save": true }, "thread_safety": "ReadSafe", "category": "LineForce", "capabilities": [ "Physics" ], "simulationAccess": true } ``` The magnitude of the force. ### Property: LineForce.MaxForce ```json { "type": "float", "access": "ReadWrite", "security": { "read": "None", "write": "None" }, "serialization": { "can_load": true, "can_save": true }, "thread_safety": "ReadSafe", "category": "LineForce", "capabilities": [ "Physics" ], "simulationAccess": true } ``` The maximum absolute force that can be applied. This property is enabled only when [InverseSquareLaw](/docs/reference/engine/classes/LineForce.md) is also enabled. This property is mainly used to address the issue that the force of the body mover becomes infinite the closer the two attachments are, causing explosions that can't be prevented by scripts. This property bounds the force's absolute value. ### Property: LineForce.ReactionForceEnabled ```json { "type": "boolean", "access": "ReadWrite", "security": { "read": "None", "write": "None" }, "serialization": { "can_load": true, "can_save": true }, "thread_safety": "ReadSafe", "category": "LineForce", "capabilities": [ "Physics" ], "simulationAccess": true } ``` Enables a reaction force (equal an opposite) to be applied to the parent of [Attachment1](/docs/reference/engine/classes/Constraint.md). By default line force only applies a force on the parent of [Attachment0](/docs/reference/engine/classes/Constraint.md) and uses [Attachment1](/docs/reference/engine/classes/Constraint.md) as the target direction without any dynamic relationship. ## Inherited Members ### From [Constraint](/docs/reference/engine/classes/Constraint.md) - **Property `Active`** (`boolean`): Indicates if the constraint is currently active in the world. - **Property `Attachment0`** (`Attachment`): The Attachment that is connected to - **Property `Attachment1`** (`Attachment`): The Attachment that is connected to - **Property `Color`** (`BrickColor`): The color of the constraint. - **Property `Enabled`** (`boolean`): Toggles whether or not the constraint is enabled. - **Property `Visible`** (`boolean`): Toggles the constraint's visibility. - **Method `GetDebugAppliedForce(bodyId: int): Vector3`**: *(deprecated)* - **Method `GetDebugAppliedTorque(bodyId: int): Vector3`**: *(deprecated)* ### From [Instance](/docs/reference/engine/classes/Instance.md) - **Property `Archivable`** (`boolean`): Determines if an Instance and its descendants can be cloned using - **Property `archivable`** (`boolean`): *(deprecated, hidden)* - **Property `Capabilities`** (`SecurityCapabilities`): The set of capabilities allowed to be used for scripts inside this - **Property `Name`** (`string`): A non-unique identifier of the Instance. - **Property `Parent`** (`Instance`): Determines the hierarchical parent of the Instance. - **Property `PredictionMode`** (`PredictionMode`): - **Property `RobloxLocked`** (`boolean`): A deprecated property that used to protect CoreGui objects. *(hidden)* - **Property `Sandboxed`** (`boolean`): When enabled, the instance can only access abilities in its `Capabilities` - **Property `UniqueId`** (`UniqueId`): A unique identifier for the instance. - **Method `AddTag(tag: string): ()`**: Applies a tag to the instance. - **Method `children(): Instances`**: Returns an array of the object's children. *(deprecated)* - **Method `ClearAllChildren(): ()`**: This method destroys all of an instance's children. - **Method `Clone(): Instance`**: Create a copy of an instance and all its descendants, ignoring instances - **Method `clone(): Instance`**: *(deprecated)* - **Method `Destroy(): ()`**: Sets the Instance.Parent property to `nil`, locks the - **Method `destroy(): ()`**: *(deprecated)* - **Method `FindFirstAncestor(name: string): Instance?`**: Returns the first ancestor of the Instance whose - **Method `FindFirstAncestorOfClass(className: string): Instance?`**: Returns the first ancestor of the Instance whose - **Method `FindFirstAncestorWhichIsA(className: string): Instance?`**: Returns the first ancestor of the Instance for whom - **Method `FindFirstChild(name: string, recursive?: boolean): Instance?`**: Returns the first child of the Instance found with the given name. - **Method `findFirstChild(name: string, recursive?: boolean): Instance`**: *(deprecated)* - **Method `FindFirstChildOfClass(className: string): Instance?`**: Returns the first child of the Instance whose - **Method `FindFirstChildWhichIsA(className: string, recursive?: boolean): Instance?`**: Returns the first child of the Instance for whom - **Method `FindFirstDescendant(name: string): Instance?`**: Returns the first descendant found with the given Instance.Name. - **Method `GetActor(): Actor?`**: Returns the Actor associated with the Instance, if any. - **Method `GetAttribute(attribute: string): Variant`**: Returns the value which has been assigned to the given attribute name. - **Method `GetAttributeChangedSignal(attribute: string): RBXScriptSignal`**: Returns an event that fires when the given attribute changes. - **Method `GetAttributes(): Dictionary`**: Returns a dictionary of the instance's attributes. - **Method `GetChildren(): Instances`**: Returns an array containing all of the instance's children. - **Method `getChildren(): Instances`**: *(deprecated)* - **Method `GetDebugId(scopeLength?: int): string`**: Returns a coded string of the debug ID used internally by Roblox. - **Method `GetDescendants(): Instances`**: Returns an array containing all of the descendants of the instance. - **Method `GetFullName(): string`**: Returns a string describing the instance's ancestry. - **Method `GetStyled(name: string, selector: string?): Variant`**: Returns the styled or explicitly modified value of the specified property, - **Method `GetStyledPropertyChangedSignal(property: string): RBXScriptSignal`**: - **Method `GetTags(): Array`**: Gets an array of all tags applied to the instance. - **Method `HasTag(tag: string): boolean`**: Check whether the instance has a given tag. - **Method `IsAncestorOf(descendant: Instance): boolean`**: Returns true if an Instance is an ancestor of the given - **Method `IsDescendantOf(ancestor: Instance): boolean`**: Returns `true` if an Instance is a descendant of the given - **Method `isDescendantOf(ancestor: Instance): boolean`**: *(deprecated)* - **Method `IsPropertyModified(property: string): boolean`**: Returns `true` if the value stored in the specified property is not equal - **Method `QueryDescendants(selector: string): Instances`**: Returns an array containing all descendants of the instance that match the - **Method `Remove(): ()`**: Sets the object's `Parent` to `nil`, and does the same for all its *(deprecated)* - **Method `remove(): ()`**: *(deprecated)* - **Method `RemoveTag(tag: string): ()`**: Removes a tag from the instance. - **Method `ResetPropertyToDefault(property: string): ()`**: Resets a property to its default value. - **Method `SetAttribute(attribute: string, value: Variant): ()`**: Sets the attribute with the given name to the given value. - **Method `WaitForChild(childName: string, timeOut: double): Instance`**: Returns the child of the Instance with the given name. If the - **Event `AncestryChanged`**: Fires when the Instance.Parent property of this object or one of - **Event `AttributeChanged`**: Fires whenever an attribute is changed on the Instance. - **Event `ChildAdded`**: Fires after an object is parented to this Instance. - **Event `childAdded`**: *(deprecated)* - **Event `ChildRemoved`**: Fires after a child is removed from this Instance. - **Event `DescendantAdded`**: Fires after a descendant is added to the Instance. - **Event `DescendantRemoving`**: Fires immediately before a descendant of the Instance is removed. - **Event `Destroying`**: Fires immediately before (or is deferred until after) the instance is - **Event `StyledPropertiesChanged`**: Fires whenever any style property is changed on the instance, including ### From [Object](/docs/reference/engine/classes/Object.md) - **Property `ClassName`** (`string`): A read-only string representing the class this Object belongs to. - **Property `className`** (`string`): *(deprecated)* - **Method `GetPropertyChangedSignal(property: string): RBXScriptSignal`**: Get an event that fires when a given property of the object changes. - **Method `IsA(className: string): boolean`**: Returns true if an object's class matches or inherits from a given class. - **Method `isA(className: string): boolean`**: *(deprecated)* - **Event `Changed`**: Fires immediately after a property of the object changes, with some