Variable assigned but it's value never used

When i press v i want the float forwardForce to change to 70.But it says it’s value is never used even though it is used in a if statement

using UnityEngine;
    using System.Collections;
    
    public class PlayerMovement : MonoBehaviour
    {
        public float jumpForce = 0;
        public float backwardForce = 0;
        public float forwardForce = 0;
        public float spinX = 0;
        public float spinY = 0;
        public float spinZ = 0;
        private Rigidbody rb;
    
        private void Start()
        {
            rb = GetComponent<Rigidbody>();
        }
    
        private void FixedUpdate()
        //Movement
        {
            if (Input.GetKeyDown("v"))
            {
                float forwardForce = 70;
            }
    
            if (Input.GetKey("w"))
            {
                rb.AddRelativeForce(0, 0, forwardForce * Time.deltaTime, ForceMode.VelocityChange);    
            }

Short Answer

 if (Input.GetKeyDown("v"))
  {
     // float forwardForce = 70; // This to
      forwardForce = 70; // This
  }

Long Answer

In the snippet above you have a class defined function called forwardForce. But when you press “v” you create a new function float forwardForce = 70. The float indicates its a new variable. Now you can’t have two variables with the same name AND the same access level. However, since you create the second forwardForce in a function it has a different access level to the previous one. It also has priority over the other one since its more local. Therefore you assign the new one to 70 then never use it again. Meaning the global one was never assigned - and that’s why you are getting the value hasn’t been assigned warning.