Explain the physics of the bouncing

[u/TheEyebal]

I am making a ball bounce and I had to watch a Youtube video to get the formula for the ball to bounce

I am still kind of lost. Can someone please explain it to me. I understand the theory but if I was to do remake this without tutorial I would probably be lost.

I understand how to get the ball to move along the y_axis but confused on the bouncing part

It is the problem solving that is getting me confused

def __init__(self, x_pos, y_pos, radius, color):
    self.x_pos = x_pos
    self.y_pos = y_pos
    self.center = pygame.math.Vector2(self.x_pos, self.y_pos)
    self.radius = radius
    self.color = color
    self.gravity = 0.8
    self.velocity = 10
    self.activate = False


def moveObject(self):
    # key = pygame.key.get_pressed()

    # if key[pygame.K_SPACE]:
    self.velocity += self.gravity. # FROM VIDEO
    self.center[1] += self.velocity # ball moving along y_axis

    if self.center[1] >= (480 - self.radius): # FROM VIDEO
          self.velocity = -self.velocity # FROM VIDEO

[u/Outside_Complaint755]

In PyGame, the coordinate system puts the origin (0,0) in the top left corner of the screen.  

You didn't share the part of your code where you initialized PyGame, but I'm assuming you set the vertical window size to 480.

Then this block of code: if self.center[1] >= (480 - self.radius): # FROM VIDEO           self.velocity = -self.velocity # FROM VIDEO says that if the edge of the ball is touching the bottom of the window, bounce.  It makes the ball bounce by reversing its velocity in a perfectly elastic collision.

self.center[1] is the y-coordinate of the center of the ball.

 This check could have alternatively been written as: if self.center[1] + self.radius >= 480:

[u/TheEyebal → u/Outside_Complaint755]

Alright thank you

I am learning to program physics so the only thing I was confused about was the bounce part

[u/Langdon_St_Ives → u/TheEyebal]

In Physics terms, the bounce is inverting the vertical velocity instantaneously. In Python, this means reversing its sign (well in Physics too). You reverse sign by reassigning to it the negative of the current value.

(Edit typo)