# mode The behavioral mode that controls the way the physics body moves and interacts with other physics bodies in a simulation. ``` var mode: PhysicsBodyMode ``` ## Discussion The property’s default value is [`PhysicsBodyMode.dynamic`](/documentation/RealityKit/PhysicsBodyMode/dynamic), which means the physics body responds to forces and can collide with all other physics bodies in the simulation. > Important: Improve the performance of your app by applying `dynamic` > mode to the physics bodies for just entities that need to interact with > all other physics bodies, because each dynamic physics body can be > computationally expensive. To configure the physics body so that an entity can move around the simulation without reacting to forces, set the property to [`PhysicsBodyMode.kinematic`](/documentation/RealityKit/PhysicsBodyMode/kinematic). Apps typically use kinematic mode for entities the app programmatically controls, such as in response to a control or a person’s interaction. For entities that don’t need to move at all, set its physics body’s mode to [`PhysicsBodyMode.static`](/documentation/RealityKit/PhysicsBodyMode/static). Physics bodies in `static` or `kinematic` mode can’t collide with other physics bodies with either mode, by default. Optionally, you can add collision support for entities that have a physics body in either static or kinematic mode by adding a [`PhysicsSimulationComponent`](/documentation/RealityKit/PhysicsSimulationComponent) to an entity that’s a common ancestor to the entities you want to collide. Then you can set [`PhysicsSimulationComponent.CollisionOptions`](/documentation/RealityKit/PhysicsSimulationComponent/CollisionOptions-swift.struct) to your preference. You can change the mode of an entity’s physics body at any time, but changing it from `static` to another mode can affect your app’s performance because the transition to a non-static mode can trigger the simulation to rebuild its state. > Tip: Set the mode of an entity’s physics body to `static` if you know > the entity doesn’t ever need to move; otherwise, set the mode to > `kinematic` or `dynamic`, even if the entity isn’t currently moving. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)