NatureOfCode

P5.js

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Forces

Friction

Mover

The Mover class is created with the parameter m. The Mover’s location, velocity and acceleration is set using the createVector(). We set the mass to m.

var Mover = function(m){
    this.location = createVector(30, 30);
    this.velocity = createVector(0, 0);
    this.acceleration = createVector(0, 0);
    this.mass = m;

The update function updates the object’s velocity and location by adding the acceleration to velocity and set the limit of the maximum velocity to 10. We then add the velocity to the location and we reset the acceleration back to zero.

    this.update = function(){
        this.velocity.add(this.acceleration);
        this.velocity.limit(10);
        this.location.add(this.velocity);
        this.acceleration.mult(0);
    }

The display function creates the ellipse at the x and y locations with a stroke and fill.

    this.display = function(){
        stroke(0);
        fill(255);
        ellipse(this.location.x, this.location.y, this.mass * 10, this.mass * 10);
    }

The checkEdge function checks if the ellipse leaves the canvas and it turns it around.

    this.checkEdge = function(){
        if(this.location.x > width || this.location.x < 0){
            this.velocity.x = this.velocity.x * -1;
        }

        if(this.location.y > height || this.location.y < 0){
            this.velocity.y = this.velocity.y * -1;
        }
    }

The applyForce function is created to add forces to the objects. Because we don’t want to affect the force vector we use a static function p5.Vector to calculate the acceleration.

    this.applyForce = function(force){
        var f = p5.Vector.div(force, this.mass);
        this.acceleration.add(f);
    }
}

Sketch

The global variable mover is added to be used in creating the objects. In the setup() function we create the canvas and we set the new Mover. The draw() function has the background and new variables called m, which is set as mass, wind and gravity which are forces.

Next we set the coefficient of friction, the normal force, the magnitude of friction and the friction using a static function and then we normalize it and multiply it by the magnitude of friction. This will determine the direction and magnitude of friction.

The functions are called from the Mover class so the mover is created.

var mover;

function setup(){
    createCanvas(650, 350);
    mover = new Mover(Math.floor(random(5, 20)));
}

function draw(){
    background(0);

    var m = mover.mass;

    var wind = createVector(0.5, 0);
    var gravity = createVector(0, 0.1 * m);

    var c = 0.5;
    var normal = 1;
    var frictionMag = c * normal;
    var friction = p5.Vector.mult(mover.velocity, -1);
    friction.normalize();
    friction.mult(frictionMag);

    mover.applyForce(friction);
    mover.applyForce(wind);
    mover.applyForce(gravity);

    mover.update();
    mover.display();
    mover.checkEdge();
}

Result: