let v;

let acc;

const q = -1.6;

const B0 = 10;

const a = 2;

const frames = 60;

const dt = 1 / frames;

let m;

​

function setup() {

  createCanvas(400, 400);

  frameRate(frames);

  pos = createVector(-2*a, 0, 0);

  v = createVector(3.2, 0, 0);

  acc = createVector(0, 0, 0);

  m = 10;

}

​

function draw() {

  translate(width/2, height / 2);

  background(220);

  acc = getAcc();

  v.add(p5.Vector.mult(acc,dt));

  pos.add(p5.Vector.mult(v,dt));

  line(0, -height/2, 0, height/2);

  line(-width/2, 0, width/2, 0);

  line(-a * 30, -height/2, -a*30, height/2);

  line(a * 30, -height/2, a*30, height/2);

  circle(pos.x*30, pos.y*30, 10);

}

​

function getB() {

  if (abs(pos.x) > a) {

    return 0

  } else if (pos.x < 0) {

    return B0

  } else {

    return -B0

  }

}

​

function getAcc() {

  c = q/m

  B = getB()

  return createVector(v.y * B,-v.x * B,0).mult(c)

}

​