Try this secret Bernoulli experiment, I guarantee you will have hours of fun with it either alone or like me if you use it at a kids science party.
Get your big adult to cut the end of the bottle at the neck so that the total length is about 5 cm or 2 inches. This should give you roughly 2.5 cm (1 inch) for the top and neck section and 2.5 cm (1 inch) for the bowl.
Bernoulli worked out that in a stream of faster moving fluid (that is gas or liquid) the pressure is less than in a slower moving fluid.
You could think of it like this: In the fast stream the volume of material, that is the total number of molecules, are stretched because they have further to go and must move faster to get there. The air that goes around the side of the ping pong ball has to go faster because it has to go around the curvature of the ball. And we know that because it has to go faster when the pressure is lower.
Now consider the top of the ball. The air there does not have to move so the pressure is normal. Not only is it normal, but it is higher than the pressure surrounding the ball. The ball can’t then move from an area of low pressure to an area of higher pressure and the higher pressure is effectively pressing it back into the bowl of the bottle.
I am sure that your friends would also like to have a go at this experiment. In fact you would be very strange if you did not challenge them to blow the ball away. However, a word of caution. Whilst it would be good to share your experiment it would be better not to share your germs as well. Wipe the neck of the bottle with your antiseptics wipes as the bottle top is passed from person to person.
There are lots more experiments that one can do with Bernoulli’s principles so keep coming back to find them!
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