Students learn about the Bernoulli effect with an amusing feat they cannot accomplish.
Bernoulli's Principle: as the speed of air increases, the pressure of that air decreases.
When you blow through the funnel, a current of fast moving air is created around and above the ball. This results in a low-pressure zone below the ball relative to its surroundings. The higher pressure air surrounding the funnel pushes the ball down and keeps it from rising any farther. The ping pong ball cannot be blown out of the funnel.
On the other hand, if you blow across the top of the ball, a low-pressure zone is created above the ball relative to its surroundings. The higher pressure air below the ball lifts up the ball.
If a steady source of air can be blown into the narrow end of the funnel (such as air being released from a large balloon), the funnel can be inverted without the ball falling out. The higher pressure room air pushes up against the ball harder than the fast flowing, low pressure air from the balloon.