# Hole in Bernoulli's theorem when trying to blow ball into bottle

According to Bernoulli's theorem while blowing a paper ball inside the bottle (as shown in this short video), the speed of the air at the mouth of bottle is higher and hence creates low pressure relative to the inside air, so the air blows from inside to outside bringing the paper out.

But when I made a hole in the bottle and repeated the same, this time the paper goes inside. Why ? The pressure at the mouth is still lower than inside while blowing. Isn't it? The pressure of the air at the hole and inside bottle should be same. Only at the mouth of the bottle is the pressure relatively lower because of higher speed (due to blowing). So, why doesn't the inside air come out through the mouth in this case ?

Also, when I replace the bottle with a tumbler with a wide mouth, the paper goes inside rather than coming out as in case of the bottle.

• The meaning of "I replace the bottle with glass" is not clear. Do you mean the original bottle was made of plastic, not glass? Or do you mean something else? Commented May 18, 2022 at 2:46
• @DavidBailey By glass I meant tumbler of wide mouth. Commented Oct 28, 2022 at 4:44
• My general comment about Bernoulli is "Whenever somebody doesn't understand a fluid dynamics problem, he blames Bernoulli, assuming that the other people in the room don't understand it either and will agree so they don't look stupid.". And no, the lift of an airfoil is not due to Bernoulli. It is simply due to momentum transfer. Flat plates fly just fine, even if they have a bit more drag. Commented Oct 28, 2022 at 5:37