I would love to be in that class.

The pressure inside the balloon would be equal to the atmospheric pressure plus the force the balloon trying to compress the atmosphere inside the balloon

@bdf2718

2 жыл бұрын

Yep. Otherwise, when you opened the neck of the balloon it would stay the same size rather than deflate. As a rough approximation, the pressure is the same. But it's not really.

Why am I just now seeing these videos, they're awesome! Your students are extremely fortunate to have you as their professor. Thank you for your hard work making these videos!

@420sakura1

6 ай бұрын

He explodes things for fun in class. Do you still want to attend

In Physics one problem which was particularly fun for the group I studied with was the hot air balloon. Using PV=nRT we solved it by saying the pressure can't change from inside to outside, just like EProf just demonstrated. So of course if you want to raise a hot air balloon you need to kick some moles out by raising T.

@420sakura1

6 ай бұрын

PV = nRR is only ideal hars. [P+ a/V°2][V-b] is the formula for real gases

Lol, so not true on the balloon. The pressure in a balloon that is stretched is absolutely higher than outside. If you disagree, can you explain to me why in fact the air comes out when you open it?

Agree, he's wrong! The pressure inside the balloon is higher than ambient pressure. What a mistake...

@rtdietrich

4 жыл бұрын

If you're very specific, then you're right, of course, because of the material's desire to pull back together. But if you're generous, you can leave the professor's statement.

@shabir301

4 жыл бұрын

Don't bother it just for simplicity neglect the balloon rubber pressure inside the video is for understanding of equation.

@mattbartley2843

4 жыл бұрын

1: Due to the rubber stretching, the balloon holds a pressure inside slightly higher than the outside air. That "gauge" pressure probably changes some depending on how much the balloon is inflated but I don't know how much. 2: When it gets as cold as liquid nitrogen, the air inside the balloon is anything but an ideal gas. The oxygen is probably the only part that still is a gas by then, in fact. But when removed the rest won't stay liquid long... So it's close enough to illustrate the concept. (If you can manage to not pop/break the balloon!)

Wrong! The balloon is made of rubber and of cause exerts a force on the gas (air) inside it when it is stretched out.

@pfisherking

4 жыл бұрын

A small amount, true. But the pressure inside the balloon is not multiples higher, so for the sake of simplicity, he assumed no pressure difference.

@Peter_Riis_DK

4 жыл бұрын

@@pfisherking Thanks - but: Don't simplify without pointing it out then. It makes the rest seem untrustworthy too.

The statement that the pressure inside the balloon and outside the balloon is absurdly false. If this were true, you would not need to tie off the balloon to keep the gas from rushing out. The elastic force of the balloon exerts pressure on the gas that opposes "runaway inflation."