A Super Toy

Note: Velocity and speed must be differentiated.
Velocity is a physical quantity which is described by the direction and absolute value of a movement.
Speed is only the 'fastness' of a movement (only the absolute value). Direction isn't taken into account.

Both balls fall downwards at the same time from one specific hight h (e.g. 1m).
First the bigger ball (blue) hits the ground. The collision between the balls and the ground is elastic. This ideal condition can only be reached if you choose rubber balls with clearly different sizes.

During the elastic collision with the ground, the big ball's direction of movement is turned around. The speed of its upwards movement is the same as during the fall. Then the small ball collides with the big ball. After this collision the small ball moves upwards with twice the speed compared to the big ball.

The big ball, however, moves with one times its speed (compared to the ground).
If we want to know the velocity of the small ball compared to the ground, we have to add the velocity of the big ball to the small ball. The direction of the velocity after the collision is upwards both times. This allows us to add the velocity of the big ball (one times compared to the ground) to the speed of the small ball (twice compared to the ground).
The resulting speed of the small ball is three times higher than its original speed.

The kinetic energy of a body is proportional to its velocity squared. Accordingly, a three times higher speed results in a nine times hihger kinetic energy. During the upwards-movement this kinetic energy is then transformed into potential energy. Because the kinetic energy is nine times higher, the ball reaches a hight that is nine times higher (than the original hight), as well. Let's say we start at an original hight of 1m. In the end the small ball will jump up into the air until it reaches 9 m!

However, in reality most collision aren't ideal. Because of this, the balls jump not that high but generally a little lower than in theory.
Why don't you try this yourself!?

	Both balls fall downwards at the same time from one specific hight h (e.g. 1m). First the bigger ball (blue) hits the ground. The collision between the balls and the ground is elastic. This ideal condition can only be reached if you choose rubber balls with clearly different sizes.
	During the elastic collision with the ground, the big ball's direction of movement is turned around. The speed of its upwards movement is the same as during the fall. Then the small ball collides with the big ball. After this collision the small ball moves upwards with twice the speed compared to the big ball.
	The big ball, however, moves with one times its speed (compared to the ground). If we want to know the velocity of the small ball compared to the ground, we have to add the velocity of the big ball to the small ball. The direction of the velocity after the collision is upwards both times. This allows us to add the velocity of the big ball (one times compared to the ground) to the speed of the small ball (twice compared to the ground). The resulting speed of the small ball is three times higher than its original speed.
	The kinetic energy of a body is proportional to its velocity squared. Accordingly, a three times higher speed results in a nine times hihger kinetic energy. During the upwards-movement this kinetic energy is then transformed into potential energy. Because the kinetic energy is nine times higher, the ball reaches a hight that is nine times higher (than the original hight), as well. Let's say we start at an original hight of 1m. In the end the small ball will jump up into the air until it reaches 9 m! However, in reality most collision aren't ideal. Because of this, the balls jump not that high but generally a little lower than in theory. Why don't you try this yourself!?