Unity 3D:如何停止在空中跳跃

using UnityEngine;

public class PlayerController : MonoBehaviour
{
    public float jumpForce = 5f;
    private bool isJumping = false;
    private Rigidbody rb;

    private void Start()
    {
        rb = GetComponent<Rigidbody>();
    }

    private void Update()
    {
        if (Input.GetKeyDown(KeyCode.Space) && !isJumping)
        {
            Jump();
        }
    }

    private void Jump()
    {
        rb.AddForce(Vector3.up * jumpForce, ForceMode.Impulse);
        isJumping = true;
    }

    private void OnCollisionEnter(Collision collision)
    {
        if (collision.gameObject.CompareTag("Ground"))
        {
            isJumping = false;
        }
    }
}