linear-velocity.md

title	description
LinearVelocity	The LinearVelocity constraint applies force on an assembly to maintain a constant velocity along a 3D vector, line, or 2D plane.

For an overview on creating, visualizing, and simulating mover constraints, including `Class.LinearVelocity`, see [Mover constraints](../../physics/mover-constraints.md). Also see [Roblox units](../../physics/units.md) to understand how Roblox units compare to metric units.

A Class.LinearVelocity constraint applies force on an assembly to maintain a constant velocity. It can be set to apply force along a Datatype.Vector3, line, or 2D plane.

The `Class.LinearVelocity` constraint applies a force that attempts to maintain a **constant** linear velocity. If you want to control the amount of force applied, use a [VectorForce](../../physics/constraints/vector-force.md) constraint. Alternatively, if you only need **initial** linear velocity, set the `Class.BasePart.AssemblyLinearVelocity|AssemblyLinearVelocity` property directly on the assembly.

Relativity

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

RelativeTo = **World** RelativeTo = **Attachment0**