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What is the Weight of Air?
As you stand in the middle of a playground or while you are sitting in your class, there is an immense weight right over your head, but you do not feel it! This is the weight of the atmosphere, or air, as we know it. Composed of nitrogen, oxygen, carbon dioxide and other gases, it surrounds the earth like an envelope. And, it extends almost a thousand kilometres above the Earth’s surface. Like all other substances, air also has weight....
What is Blood Pressure?
The heart is a live pump that delivers blood to different parts of the body. Blood flows in or flows out when the heart contracts and expands. The blood is forced into the arteries, which expand to receive the oncoming blood. The force with which the blood moves through the arteries is knows as blood pressure. The arteries have a muscular lining which resists this pressure. The blood is thus squeezed out into smaller blood vessels....
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