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Photo: With a few mighty blasts from the gas burner, this hot-air balloon safely cleared these tall trees. Hot-air balloons float in the sky for pretty much the same reason that boats float on the sea. A boat floats because it's supported by the water beneath it: the weight of the boat pulling downward is exactly counterbalanced by the pressure of the water beneath it pushing upward. A boat doesn't float perfectly on the water surface but sinks partly into the water according to how heavy it is.
The bigger the boat, the bigger the area of water beneath it, the greater the force of the water pressure pushing upward on it, and the more weight it can carry. Here's another way to look at it: generally speaking, an object will float if it's less dense than water in other words, lighter than an equal volume of water and sink if it's more dense heavier than an equal volume of water. Imagine a block of lead the size of your arm dropped into a bathtub filled with water. An "armful of lead" weighs much more than an "armful of water" so lead sinks to the bottom of the tub straight away.
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But an "armful of plastic"—the plastic arm of a manikin, for example—floats because it weighs less than the same volume of water. Animation: Burning gas makes the air inside the balloon less dense, producing an upward force or lift. In this case, the weight of the balloon blue arrow is greater than the lift red arrow. A hot-air balloon isn't like a rubber balloon tied in a knot: it's open at the bottom so air can still get in and out.
That means the density of the air in the balloon can change while the pressure inside and outside is essentially the same. Hot-air balloons float because the air caught inside the balloon is heated up by a burner, making it less dense than the air outside. As the burner heats the air, it expands and some of the air escapes; that's what makes it less dense.
Here's another way to think of it. You've probably heard people say that heat rises, by which they really mean that hot air rises. When you see clouds of dirty gray gas drifting upward from smokestacks, that's because the air coming out of them is hotter than the ambient surrounding air. If you could wrap a bag around the hot air entering the bottom of a smokestack, and seal it up, the whole bag would shoot upward and come out of the top before zooming off and up into the air. In effect, you'd have made a tiny little hot air balloon!
Tiny balloons aren't actually much use, however. If you want to carry a heavy weight on the sea, you need a big ship: one that can displace more water can carry more load. In exactly the same way, you need a big hot-air balloon to lift a big weight—because you need to create more lift with a larger volume of hot gas. That explains why hot-air balloons are generally so large. If you know that warm air rises, you could build yourself a hot-air balloon without knowing anything more about science—in other words, just by trial and error.
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What do you need to build a hot air balloon in practice? Three things: an envelope, a burner, and a basket. Photo: Envelopes: Look at the little people in the center of this picture and you can see just how big these envelopes are. Note the gores the curved, vertical strips from which the envelopes are sewn together.
To trap you some hot air, you'd need the balloon itself, which ballooners generally call the envelope.
These days, it's usually made from a strong, light, durable, synthetic fabric such as ripstop nylon nylon sewn into squares to stop rips and tears from spreading. The envelope is made in vertical sections called gores that are sewn together very tightly at the seams to make a strong, air-tight container that doesn't leak. There are holes in the envelope at both the top and the bottom: the top of the balloon, known as the crown , has a little hole in it called the parachute vent or parachute valve that can be opened by pulling on a cord, which allows hot air to escape and makes the balloon descend.
The hot air that fills the envelope comes from gas jets fueled by propane cylinders similar to ones you might use on a portable camping stove. Although some balloons have only a single burner, it's more common to have two or more, both to provide more lift and for safety's sake in case one burner fails. Each fuel cylinder provides about 70—90 liters of fuel, and weighs about 50—60kg —lb when full.
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Add to Shopping List. Frequently bought with Revlon Colorsilk Beautiful Co Garnier Nutrisse Nourishing H Walgreens Beauty Silicone Rub Sally Hansen Hard as Nails Xt Scunci Effortless Beauty No D L'Oreal Paris Feria Permanent Garnier Nutrisse Ultra Color Goody Girls' Bright Bow Salon L'Oreal Paris Superior Prefer L'Oreal Paris Excellence Crem Conair Brush Detangle and Sty Scunci Mini Metal Rhinestone Takis Fuego Tortilla Chips Ho On The Move Spray Bottl Vaseline Lip Balm Mini Rosy Keeping rubber bands cool helps maintain their flexibility.
A rubber band is weakened and often useless after being exposed to heat. That is when we throw it away. We humans need to watch that we do not become hot-headed. It is best to be vigilant to heated arguments and hot conflict. Or be prepared with conflict resolution and relaxation skills.
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Mindfulness and practices of meditation can also help. We function best when we are able to keep cool under adverse situations. Fortunately, we are not rubber bands. When we snap, crack or break we do not end up in a garbage bin. We can access help and get back on track. We can bounce back stronger after our personal and professional walks through fire. Rubber bands demonstrate resilience. We show even more flexibility, bounce-ability and spring, especially when we practice basic hardiness and wellness strategies.
The result is increased confidence, flexibility, health and vitality. For organizational bottom lines, this means improved results in adaptability to business change and improved employee productivity, problem-solving, collaboration, retention and work satisfaction. For families, it means an opportunity for members to flourish. If you stretch a rubber band to its maximum, it usually springs back. That is because rubber bands are primarily made from natural rubber. Natural rubber has a superior elasticity. It is made up of minute threads that, when stretched, untwist and unbend, sort of like, becoming unglued.