Initialize velocities in all constructors.
Clear background in draw function.
Add Ball constructor with angle and velocity.
Move the image to (x,y) instead of (0,0).
Increase size of window.
Change image mode to CENTER.
This way, the circle and the image will have the same coordinates.
Move gravity initialization to beginning.
This way, don't have to have default value so many times.
Add function to ball for printing its location.
Move r initialization to top.
It's the same every time.
Change framerate back to 100.
Revise gravity constant to a much lower value.
Each pixel is not necessarily a meter. In fact, given the size of the ball, it most certainly is not.
Add velocity to the ball.
Set defaults for velocities at top.