You can't get a leaf to move to the edge of a pond by throwing stones behind it because of Newton's Third Law of Motion.

Here's why:

* Action and Reaction: Newton's Third Law states that for every action, there is an equal and opposite reaction. When you throw a stone behind the leaf, it exerts a force on the water, pushing it forward.

* Leaf's Response: The water, in turn, exerts an equal and opposite force on the leaf. This force pushes the leaf away from the direction of the stone's motion.

* Result: Instead of moving towards the edge of the pond, the leaf will actually be pushed *further away* from it.

Think of it like this: If you push a wall, the wall pushes back on you with the same amount of force. The leaf is like the wall in this scenario. It's the water that gets pushed, and the leaf reacts to that force.