Jumping in Unity by AddForce

I'm recently started working with physics in Unity and I need to let my character jump.
I want to do it by AddForce() but I also need to check is the character grounded.
In the code I'm checking it with time.
Here is my code:

private void JumpByForce() 
{
    time_after_jump = Time.time + 1f;
    Debug.Log(time_after_jump);

    if (Time.time > time_after_jump)
    {
        isJumping = true;
    }
    if (isJumping)
    {
        Player.GetComponent<Rigidbody2D>().AddForce(new Vector2(0, 750));
        isJumping = false;
    }
}

private void Start()
{
    Player_pos_x = Player.transform.position.x;
    Player_pos_y = Player.transform.position.y;
    isJumping = true;
    
}

I thought that I wrote a right code, but in console isn't appearing what I want.
(It's printing time_after_jump without adding + 1f).
At the first time when I'm clicking on the jump button the Player Jumping correctly.But the following times it isn't jumping.
My biggest question Is - Why time_after_jump printing without
(+ 1f)?

Debug.Log() prints the final value, not the expression in the variable. In your situation, it prints the final value of time_after_jump. Unity calculates that value on the previous line and then prints it (So instead of printing 10+1 it prints 11).

Also, the reason your player doesn't jump after the first time is because Time.time will never be greater than time_after_jump since you are adding 1 to it before the check, therefore the first if is never triggered, and therefore isJumping is never true apart from the first time when you initialize it with the value true.

I believe I have figured out the problem here. if(Time.time > time_after_jump) while always return false.

Let's say Time.time = 2. And time_after_jump = Time.time + 1. Then time_after_jump = 3. Meaning it is always greater.

Try this instead:

time_after_jump = Time.time;
Debug.Log(time_after_jump);

if ((Time.time + 1f) > time_after_jump)
{
    isJumping = true;
}

Although, personally I would use time.deltaTime, create a timer, and reset the timer value when jumping, so as to set isJumping to false.

E.g:

time_after_jump += Time.deltaTime; 
if(time_after_jump > timeJumping)
{
  isJumping = true;
}

if(isJumping)
{
   //Movement here
   time_after_jump = 0;
   isJumping = false;
}

However, this would be a lot simpler if you used an Input to get the jump. Then you would reset the timer when jump is pressed.

Am at work, so this is untested, but I hope you get the idea. Happy coding.

To make the character jump by AddForce with time I've must check time_after_jump in FixedUpdate method and if Time.time will more than time_after_jump, than isJumping will be true and I can again jump our character.

I used this code:

private void JumpByForce() 
{
    if (isJumping)
    {
        time_after_jump = Time.time + 0.8f;
        Player.GetComponent<Rigidbody2D>().AddForce(new Vector2(0, 750));
        isJumping = false;
    }
}

private void FixedUpdate()
{
    if (Time.time > time_after_jump)
    {
        isJumping = true;
    }
}