Why balloons rise

As Isaac Newton explained years ago , a body at rest or in motion tends to stay that way until acted upon by an outside force. So let's say you're driving forward at 40 miles per hour and you accelerate to 55 mph, feeling yourself pressed back into the seat.

What's actually going on is that your body wants to stay at the constant speed of 40 mph but the car starts going faster than that, catching up to you and running into your back. Consider the opposite situation.

You're driving along at a constant speed but something rabbit, deer, or child runs in front of your path. You slam on the brakes, quickly decelerating and getting thrown forward. Your body was totally happy traveling at a constant speed and wanted to keep doing so. But the car around it suddenly slowed down, falling behind you and leaving you dangling in the air. Now, if you play out any of these same situations with a helium balloon in the car, you'll notice something peculiar.

Whenever you get pushed backwards, the balloon goes forward. If you get thrown forward, the balloon goes back. And, if you make a sharp turn , you lean outward while the balloon leans inward. It's like the balloon always wants to do the opposite of what you're doing. I was surprised to see the sensitivity to a couple of meters as well. You are commenting using your WordPress.

You are commenting using your Google account. You are commenting using your Twitter account. You are commenting using your Facebook account. Notify me of new comments via email. Notify me of new posts via email. Blog at WordPress. Protons for Breakfast. Why do Helium balloons rise? Druck DPI Barometer. Share this: Twitter Facebook.

If you want to lift a certain weight larger than the lift force of the balloon what is better, to take more balloons of the same size or to take a larger balloon? If you take one large balloon with the double diameter you also need 8 times the helium. But the weight of the balloons hull is only 4 times the weight of the small balloon.

So you get a little more lift force from the one large balloon compared to the 8 small balloons using the same amount of expensive helium. Lots of good answers here, but none address the main issue with your questions. The balloon doesn't rise due to any direct mechanism. Instead, the denser air around the balloon pushes itself down, with the net effect pushing the balloon up. This is similar to the misstatement that 'heat rises'. Again, it doesn't.

Instead, cold falls, pushing the heat up. Edited: someone also mentioned surface tension and that would be as for example all around the ballon the atmospheric pressure exerted a force right? Sign up to join this community. The best answers are voted up and rise to the top.

Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Learn more. Why does a helium balloon rise? Asked 2 years, 5 months ago. Active 2 years, 5 months ago. Viewed 9k times. Improve this question.

BioPhysicist When the balloon is filled, it normally has a very large volume of helium compared to the volume of the rubber. Are you suggesting that in an empty balloon, there is the same vacuum as we'd find in outer space?

Or do you think there is some air in there? This is not the same as having a vacuum, as an empty balloon also has no volume. Show 10 more comments. Active Oldest Votes. Improve this answer. CJ Dennis 7 7 silver badges 14 14 bronze badges.

BioPhysicist BioPhysicist On the show Mythbusters, they were able to make a very large balloon out of lead foil that floated in air. Instead of explaining, you just start with an equation "you will usually see" and manipulate terms. The OP is obviously confused with the idea you usually hear about less dense rising and more dense sinking, so I addressed this concern.

Had the OP asked about pressure gradients I would have addressed that And I think the OP knows that a blown up balloon has its helium contained. I did not write the answer for you, I wrote it for the OP, which is evident by the fact that they accepted this answer. I think it's better to address the misconception behind the actual question. You are more than welcome to write up your own answer if you don't like mine, but I find it odd that you seem to suggest an answer that is already accepted isn't good enough and even going as far as to comment this on other answers.

Add a comment. An empty ballon with no air in it falls If you have a balloon of the same volume as the helium balloon, but with no air in it, then it will float. Acccumulation Acccumulation 7, 12 12 silver badges 29 29 bronze badges. And that support means more mass, which in turn means higher density and you're back to square one. It doesn't help that while we have many lightweight materials that are very strong in tension, we don't have much that's lightweight and strong in compression especially with regards to buckling.

The Mythbusters had to work hard to create that result intentionally, and even then had to put a dent in the tanker before pumping a nearly full vacuum. After disabling safety valves etc. S14E02 Tanker Crush mythresults. They declared the myth "busted". If you've seen multiple videos, presumably they were from very different rail tankers, because the spherical symmetry of real ones makes them very strong under uniform compression of atmospheric pressure.

The myth was busted, but that's not the same as what we're talking about. Rail tankers are built to withstand atmospheric pressure - but they also don't rise in the air even with the best vacuum we can do , because they're too heavy for their volume.

The tricky part is finding something strong enough to resist atmospheric pressure while at the same time being lightweight enough to create enough buoyancy to outstrip its own weight not to mention allow carrying payloads etc. Other than that yes it's a helpful explanation of why using He or H2 pressure to oppose atmospheric pressure is useful for creating lift, even though they're not massless.