​

function setup() {

  createCanvas(400, 400);

  pendulum1 = new Pendulum(createVector(width/2,0));

}

​

function draw() {

  background(220);

  pendulum1.update();

  pendulum1.show();

}

​

class Pendulum{

  constructor(origin){

    this.length = 175;

    this.origin = createVector(origin.x,origin.y);

    this.bob = createVector(this.origin.x,this.length); 

    this.angle = PI/4;

    this.angleAcc = 0;

    this.angleVel = 0;

    this.size = 32;

    this.mass = 1;

  }

  update(){

    //Fp = Fg * sin(theta)

    this.angleAcc = -0.01 * this.mass * sin(this.angle);

    this.angle += this.angleVel;

    this.angleVel += this.angleAcc;

    this.angleVel *= 0.97;

    this.bob.x = this.origin.x + this.length*sin(this.angle);

    this.bob.y = this.origin.y + this.length*cos(this.angle);

  }

  show(){

    stroke(0);

    fill(100);

    line(this.origin.x,this.origin.y,this.bob.x,this.bob.y);

    circle(this.bob.x,this.bob.y,this.size);

  }

}