For one of our 3D animation practise tasks, we had to create a simple bouncing ball, then after we finished that task, we could animate balls of different weights or we could even give the ball a bit of character and animate it looking sad/happy etc.

Here's my attempt at the simple bouncing ball:

I think this looks ok! But perhaps the arc and movement of the ball could be a little better. Perhaps I could have exaggerated the squash and stretch a little more too.

Here's my attempt at animating a heavy ball, like a bowling ball:

I also think this animation is ok. The falling speed of the ball should probably be a little faster though, to emphasize that it's a heavy ball.

Here's my attempt at animating a 'sad' ball:

Hopefully you can tell in the video that I slowed down the ball as it bounced and made it spend more time squished on the ground. This was to try and make it seem down and a bit sad.

I think maybe next time I should try making the squash and stretch even more exaggerated in order to show more clearly that the ball is supposed to be upset.