Gravity and mass

The force exerted by gravity increases propotionally with mass. This offsets the increase in force required for objects with larger mass.

So I've removed the hard limit on the minimum height in order to make the balls all bounce in a regular fashion. This means they will gradually loose vertical momentum (and sink into the floor given enough time...). How do I avoid this, while also keeping all the ball bouncing evenly?

var wind, balls = [], step = Math.round(Math.random() * 1000);

function Ball() {
  this.radius = Math.random() * 64;
  this.diameter = this.radius * 2;
  this.position = createVector(width/2, 100 - this.radius);
  this.velocity = createVector(0, 0);
  this.acceleration = createVector(0, 0);
  this.mass = this.radius / 64;
  // gravity force is proportional to mass
  this.gravity = createVector(0, this.mass * 0.1);
}
Ball.prototype.render = function() {
  stroke(0);
  fill(200, 200, 200, 200);
  ellipse(this.position.x, this.position.y, this.diameter, this.diameter);
};
Ball.prototype.move = function() {
  this.velocity.add(this.acceleration);
  this.position.add(this.velocity);
  this.acceleration.mult(0);
  this.bounce();
};
Ball.prototype.bounce = function() {
  if (this.position.y > height - this.radius) {
    this.velocity.y = Math.abs(this.velocity.y) * -1;
  }
  if (this.position.x < this.radius) {
    this.velocity.x = Math.abs(this.velocity.x) / 2;
  } else
    if (this.position.x > width - this.radius) {
    this.velocity.x = Math.abs(this.velocity.x) * -1 / 2;
  }
};
Ball.prototype.applyForce = function(force) {
  force = force.copy();
  force.div(this.mass);
  this.acceleration.add(force);
};

function createWind() {
  step = step + 0.003;
  wind = noise(step) - 0.5;
  return createVector(wind / 50, 0);
}

function plotWind(windVec) {
  var windWidth = windVec.x * width * 50;
  rect(width/2, 0, windWidth, 10);
}


function setup() {
  var i = 10;
  createCanvas(500, 400).parent('canvas-container');
  wind = createWind();
  while (i--) {
    balls.push(new Ball());
  }
}

function draw() {
  var i = balls.length;
  background(255);
  while (i--) {
    balls[i].render();
  }
  plotWind(wind);
  update();
}

function update() {
  var ball, i = balls.length;
  wind = createWind();
  while (i--) {
    ball = balls[i];
    ball.applyForce(ball.gravity);
    ball.applyForce(wind);
    ball.move();
  }
}