// The Coding Train / Daniel Shiffman

// https://thecodingtrain.com/CodingChallenges/159-simple-pendulum-simulation.html

// https://youtu.be/NBWMtlbbOag

// https://editor.p5js.org/codingtrain/sketches/SN-39sHAC

​

let angle;

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let angleV = 0;

let angleA = 0;

​

let bob;

let len;

let origin;

​

let gravity = 1;

​

function setup() {

  createCanvas(600, 600);

  origin = createVector(300, 0);

  angle = PI / 4;

  bob = createVector();

  len = 200;

}

​

function draw() {

  background(0);

​

  let force = gravity * sin(angle);

  angleA = (-1 * force) / len;

  angleV += angleA;

  angle += angleV;

​

​

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

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

​

  stroke(255);

  strokeWeight(8);

  fill(127);

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

  circle(bob.x, bob.y, 64);

}

​