How do I make a ball bounce normally in a box?

I want to try to make a lot of balls bounce inside a box.
I start with one ball with motion.
Two extreme things happens. One is faster and faster. The other is slow down and just rotates.

How do I get a correct physics simulation?

please help, and thank you

brownian2.blend (5.29 MB)

  1. Your gravity is set to 0.
  2. Only one of the spheres has rigid body applied.

I corrected the gravity and the one sphere falls as expected. Not sure what else you are expecting help on.