Can u explain the working of a hot air balloon on the basis of this activity
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How does a hot-air balloon work (in theory)?
In a word: buoyancy.
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 waterbeneath it: the weight of the boat (pulling downward) is exactlycounterbalanced 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. But an "armful of plastic"—the plasticarm of a manikin, for example—floats because it weighs less than the same volume of water.
Hot-air balloons float because the air trapped inside the balloon is heated up by a burner, making it less dense than the air outside. Here's another way to think of it. You've probably heard people say that heat rises, by which they really mean that hot airrises. 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!
In a word: buoyancy.
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 waterbeneath it: the weight of the boat (pulling downward) is exactlycounterbalanced 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. But an "armful of plastic"—the plasticarm of a manikin, for example—floats because it weighs less than the same volume of water.
Hot-air balloons float because the air trapped inside the balloon is heated up by a burner, making it less dense than the air outside. Here's another way to think of it. You've probably heard people say that heat rises, by which they really mean that hot airrises. 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!
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