# How to make a rigidbody hover giving it an upward force? Mine still doesn't stay even when the upward force and graviational pull are equal.

I am trying to simulate a helicopter. Just now started with it. As a trial I took a cube, applied rigidbody to it setting its mass as 2. I then applied a constant force of 19.6 (since 2 * 9.8 = 19.) upwards. What I anticipated was that it would not move since upward and downward forces are exactly equal, but it actually moves downwards(though very slowly).
Increasing the force by any amount moves it upwards. Am I wrong with the physics part or there is any else. Someone please help.

Something like this

``````	void FixedUpdate(){
float yVel = rigid.velocity.y + Physics.gravity.y;

//Howering

//Altitude
}
``````

hi Iqu,
I’ve done this so many times that I’ve lost the count of it.
Jokes apart, here’s what I’ve done for mine:

``````function FixedUpdate () { //you have to apply the force Always in FixedUpdate function, otherwise in the Update
// function the force is not applied costantly, resulting in a slow fall towards the ground

//Here we apply a force to the rigidbody's local up vector and we multiply it by the rigidbody mass
//and the Absolute gravity up force.
//for now it should give you a go as long as your rigidbody doesn't tilt  :S

rigidbody.AddRelativeForce( Vector3.up * (rigidbody.mass * Mathf.Abs(Physics.gravity.y) ) );

//How simple is that ?
}
``````

if you need more info on helicopter’s Physics just ask me, I’m developing a physics based helicopter game

Force and Gravitational acceleration is two different things. Force is applied with consideration of the object’s mass while Gravity ignores mass. Try using Acceleration as the Forcemode: http://docs.unity3d.com/ScriptReference/ForceMode.html and you should get it to hover still. Although forcemode acceleration is probably not what you want to control your helicopter.

Normally a helicopter probably has to recalculate how much force it needs to apply to hover still. If it detects it moves upwards it has to decrease force and when it detects it moves down it has to increase force.