# VelocityChange > Add an instant velocity change to the rigidbody, ignoring its mass. ## Definition * **Type:** Field * **Namespace:** [UnityEngine](/engine/6000.0/script-reference/unityengine.md) * **Assembly:** UnityEngine.PhysicsModule ```csharp VelocityChange = 2 ``` ### Remarks Apply the velocity change instantly with a single function call. In contrast to [ForceMode.Impulse](/engine/6000.0/script-reference/unityengine/forcemode/impulse.md), VelocityChange will change the velocity of every rigidbody the same way regardless of differences in mass. This mode is useful for something like a fleet of differently-sized space ships that you want to control without accounting for differences in mass. In this mode, the unit of the force parameter is applied to the rigidbody as distance/time. ### Examples ```csharp using UnityEngine; public class ForceModeExample : MonoBehaviour { //Use to switch between Force Modes enum ModeSwitching { Start, Impulse, Acceleration, Force, VelocityChange }; ModeSwitching m_ModeSwitching; Vector3 m_StartPos, m_StartForce; Vector3 m_NewForce; Rigidbody m_Rigidbody; string m_ForceXString = string.Empty; string m_ForceYString = string.Empty; float m_ForceX, m_ForceY; float m_Result; void Start() { //You get the Rigidbody component you attach to the GameObject m_Rigidbody = GetComponent(); //This starts at first mode (nothing happening yet) m_ModeSwitching = ModeSwitching.Start; //Initialising the force which is used on GameObject in various ways m_NewForce = new Vector3(-5.0f, 1.0f, 0.0f); //Initialising floats m_ForceX = 0; m_ForceY = 0; //The forces typed in from the text fields (the ones you can manipulate in Game view) m_ForceXString = "0"; m_ForceYString = "0"; //The GameObject's starting position and Rigidbody position m_StartPos = transform.position; m_StartForce = m_Rigidbody.transform.position; } void FixedUpdate() { //If the current mode is not the starting mode (or the GameObject is not reset), the force can change if (m_ModeSwitching != ModeSwitching.Start) { //The force changes depending what you input into the text fields m_NewForce = new Vector3(m_ForceX, m_ForceY, 0); } //Here, switching modes depend on button presses in the Game mode switch (m_ModeSwitching) { //This is the starting mode which resets the GameObject case ModeSwitching.Start: //This resets the GameObject and Rigidbody to their starting positions transform.position = m_StartPos; m_Rigidbody.transform.position = m_StartForce; //This resets the velocity of the Rigidbody m_Rigidbody.velocity = new Vector3(0f, 0f, 0f); break; //These are the modes ForceMode can force on a Rigidbody //This is Acceleration mode case ModeSwitching.Acceleration: //The function converts the text fields into floats and updates the Rigidbody’s force MakeCustomForce(); //Use Acceleration as the force on the Rigidbody m_Rigidbody.AddForce(m_NewForce, ForceMode.Acceleration); break; //This is Force Mode, using a continuous force on the Rigidbody considering its mass case ModeSwitching.Force: //Converts the text fields into floats and updates the force applied to the Rigidbody MakeCustomForce(); //Use Force as the force on GameObject’s Rigidbody m_Rigidbody.AddForce(m_NewForce, ForceMode.Force); break; //This is Impulse Mode, which involves using the Rigidbody’s mass to apply an instant impulse force. case ModeSwitching.Impulse: //The function converts the text fields into floats and updates the force applied to the Rigidbody MakeCustomForce(); //Use Impulse as the force on GameObject m_Rigidbody.AddForce(m_NewForce, ForceMode.Impulse); break; //This is VelocityChange which involves ignoring the mass of the GameObject and impacting it with a sudden speed change in a direction case ModeSwitching.VelocityChange: //Converts the text fields into floats and updates the force applied to the Rigidbody MakeCustomForce(); //Make a Velocity change on the Rigidbody m_Rigidbody.AddForce(m_NewForce, ForceMode.VelocityChange); break; } } //The function outputs buttons, text fields, and other interactable UI elements to the Scene in Game view void OnGUI() { //Getting the inputs from each text field and storing them as strings m_ForceXString = GUI.TextField(new Rect(300, 10, 200, 20), m_ForceXString, 25); m_ForceYString = GUI.TextField(new Rect(300, 30, 200, 20), m_ForceYString, 25); //Press the button to reset the GameObject and Rigidbody if (GUI.Button(new Rect(100, 0, 150, 30), "Reset")) { //This switches to the start/reset case m_ModeSwitching = ModeSwitching.Start; } //When you press the Acceleration button, switch to Acceleration mode if (GUI.Button(new Rect(100, 30, 150, 30), "Apply Acceleration")) { //Switch to Acceleration (apply acceleration force to GameObject) m_ModeSwitching = ModeSwitching.Acceleration; } //If you press the Impulse button if (GUI.Button(new Rect(100, 60, 150, 30), "Apply Impulse")) { //Switch to impulse (apply impulse forces to GameObject) m_ModeSwitching = ModeSwitching.Impulse; } //If you press the Force Button, switch to Force state if (GUI.Button(new Rect(100, 90, 150, 30), "Apply Force")) { //Switch to Force (apply force to GameObject) m_ModeSwitching = ModeSwitching.Force; } //Press the button to switch to VelocityChange state if (GUI.Button(new Rect(100, 120, 150, 30), "Apply Velocity Change")) { //Switch to velocity changing m_ModeSwitching = ModeSwitching.VelocityChange; } } //Changing strings to floats for the forces float ConvertToFloat(string Name) { float.TryParse(Name, out m_Result); return m_Result; } //Set the converted float from the text fields as the forces to apply to the Rigidbody void MakeCustomForce() { //This converts the strings to floats m_ForceX = ConvertToFloat(m_ForceXString); m_ForceY = ConvertToFloat(m_ForceYString); } } ```