Add weight to ball

Question

I'm having troubles with the weight of a ball. I can apply gravity and a bouncing level, but I don know how to add weight. I want to do a "rock ball" and a "rubber ball", to compare it's bouncing visually.

I coded that function which is called every half second:

    this.applyGravity = function(gravity, bouncingLevel){
        this.ySpeed += gravity;
        this.move(0, this.ySpeed);

        if(this.getY() + this.getHeight() > this.bottomBoundary)
        {
            this.setY(this.bottomBoundary - this.getHeight());
            this.ySpeed = 0;
            this.counter = 0;
        }
    }

Thanks for your help and time, GaL

You want to add "mass" and then just plug mass into any of the basic Newtonian equations you use to determine velocity, etc. Of course, as everyone who has passed high school physics knows, the mass of an object does not affect the force of gravity on it. — Ed S., Apr 21 '13 at 22:09
Sorry to say that I never saw physics in school... We had (and maybe have) a bad education system in Argentina. So, I will read about it. — gal007, Apr 24 '13 at 19:09

markE · Answer 1 · 2013-04-22T00:04:35.973

Your “bouncingLevel” is commonly called “restitution” and is applied to an object that is colliding.

Restitutions typically range from 0.0 – 1.0.

1.0 means the object is absolutely bouncy—so it loses no speed during a collision.

0.0 means the object loses all it’s speed during a collision—so it “splats” and doesn’t bounce at all.

Here’s how you add restitution to your collision:

Warning: I have not tried my code below…just off the top of my head—you may need to debug!

// create a flag to tell us whether we are currently colliding
var isColliding=false;

// Create a "squash"
// When an object collides, it can get shorter/fatter
// This squash variable simulates the object as it un-squashes
var squash=0;

this.applyGravity = function(gravity, bouncingLevel){

if(isColliding){

    // un-squash the object at ySpeed
    // note: ySpeed should be negative at this point
    squash += this.ySpeed;

    // if we're all un-squashed, show the object's motion again
    if(squash<0){
        // since squash<0 the object will now rise
        // above the boundary and start moving upward
        this.setY(this.getHeight+squash);
        // all done colliding...clear the flag
        isColliding=false;
    }

    return;
}

this.ySpeed += gravity;
this.move(0, this.ySpeed);

if(this.getY() + this.getHeight() > this.bottomBoundary)
{
    // set the new after-collision speed
    this.ySpeed = -this.ySpeed*bouncingLevel;

    // set the collision flag
    isColliding=true;

    // calculate squash:
    // == how far the object's momentum carried it into the boundary
    squash = this.getY() + this.getHeight();

    // visually set the object on bottomBoundary until it "rebounds"
    // alternatively, you could let it visually fall under the boundary
    this.setY(this.bottomBoundary - this.getHeight());

    this.counter = 0;
}

}

Add weight to ball

1 Answers1