# Bouncing Ball Velocity Problem

**URL:** <https://discourse.processing.org/t/bouncing-ball-velocity-problem/27620>\
**Category:** Coding Questions\
**Created:** [February 6, 2021, 8:16am UTC](https://discourse.processing.org/t/bouncing-ball-velocity-problem/27620 "2021-02-06T08:16:10Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![Akiraishido](https://avatars.discourse-cdn.com/v4/letter/a/eada6e/32.png) [@Akiraishido](https://discourse.processing.org/u/Akiraishido)\
**Post date:** [February 6, 2021, 8:16am UTC](https://discourse.processing.org/t/bouncing-ball-velocity-problem/27620/1 "2021-02-06T08:16:10Z")

</div>

I’m new to Processing (I programmed in C# before) and I tried to make a bouncing ball with vectors but when I run the program, the ball goes a little bit to the right.  
This is my code:

```auto
Ball b;

void setup() {
  size(1280, 720);
  b = new Ball(0, height/2, 3, 2, 30);
}

void draw() {
  background(0);
  b.Display();
  b.Update();
  b.Limit(4);
  b.Bounce();
}

```

and my Ball class;

```auto
class Ball {

  PVector pos, vel, acceleration;
  float radius;

  Ball(float x, float y, float spdx, float spdy, float size) {
    pos = new PVector(x, y);
    vel = new PVector(spdx, spdy);
    acceleration = new PVector(-0.01, 0.1);
    radius = size/2;
  }

  void Update() {
    vel.add(acceleration);
    pos.add(vel);
  }
  void Display() {
    circle(pos.x, pos.y, radius*2);
  }
  void Limit(float max) {
    if (max > 10) {
      vel.normalize();
      vel.mult(max);
    }
  }
  void Bounce() {
    if (pos.x < 0 || pos.x > width) {
      vel.x = vel.x * -1 + 0.5;
    }
    if (pos.y < 0 || pos.y > height) {
      vel.y = vel.y * -1 + 0.5;
    }
  }
}

```

I can’t find a solution to problem, despite my tries, so is there a solution?  
Thanks!  
(I’m French, so sorry for my english)

---

<div class="post-metadata">

**Author:** ![CodeMasterX](https://yyz2.discourse-cdn.com/flex036/user_avatar/discourse.processing.org/codemasterx/32/2942_2.png) [@CodeMasterX](https://discourse.processing.org/u/CodeMasterX)\
**Post date:** [February 6, 2021, 11:50am UTC](https://discourse.processing.org/t/bouncing-ball-velocity-problem/27620/2 "2021-02-06T11:50:16Z")

</div>

> [@Akiraishido](#):
>
> `acceleration = new PVector(-0.01, 0.1);`

here is the issue.When I combined your code, it continuously went to the right. It is because you see acceleration PVector to -0.01,0.1. -0.01 is the force pushing the ball to the left and the 0.1 is the gravity

---

<div class="post-metadata">

**Author:** ![Akiraishido](https://avatars.discourse-cdn.com/v4/letter/a/eada6e/32.png) [@Akiraishido](https://discourse.processing.org/u/Akiraishido)\
**Post date:** [February 6, 2021, 11:51am UTC](https://discourse.processing.org/t/bouncing-ball-velocity-problem/27620/3 "2021-02-06T11:51:10Z")

</div>

Yes, it works now!  
Thanks!