To make jumping, falling and throwing objects look realistic, you need to include real-world effects like gravity. This video shows you how to add gravity to a bouncing ball. Download the Scratch 2.0 code: simple_gravity
Friction
To make movement look realistic, you need to include real-world effects, like friction, in your Scratch games. This video shows you a simple way to include friction in the way your objects move. Download the Scratch 2.0 code: friction