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30% off (Sale price $225.00, Reg. Price $325.00) :: The Deal $225 for Aquatic Bubble-Ball Rental for up to 2 Hours ($325 value)Life Jackets: How Do They Keep Us Afloat?A life jacket is like a magic suit of armor that turnsintimidating bodies of water into fun, helpful friends. Learn how life jacketswork with Groupon’s exploration of flotation.Archimedes, a bathtub, and the crown of a suspicious king—those whosephysics teachers had a fondness for the Greeks may vaguely recall that thesehave something to do with flotation. The first, supposedly first noticed by theGreek physicist splashing around in his bath, is that submerged bodies displacea volume of water equal to their own volume. The second is what’s appropriatelyknown as Archimedes’s principle, and was purportedly used by the man todetermine, by comparing densities, whether a goldsmith had substituted somesilver into a king’s crown. This principle states that a body is buoyed up by aforce equal to the weight of the fluid itdisplaces.An example may help demonstrate how these two pieces of informationwork together to keep us from drowning. Imagine a very small, very heavy teddybear that weighs 10 pounds. When placed in water, the bear displaces its ownvolume—what equals 64 cubic inches. That same amount of water, however, weighsonly 2.3 pounds, so the water’s buoyant force is not enough to counteract the10 pounds of force pressing down from the teddy bear’s weight, thus the bearsinks. Now, suppose we place the bear on a raft weighing 1 pound but which has avolume of 240 cubic inches. Two hundred forty cubic inches of water weighsabout 8.7 pounds. If we add together 8.7 and 2.3 pounds, the combined weight ofthe water displaced by the bear and the raft, we get a total buoyant force of11 pounds, precisely the weight needed to keep the bear and its raft afloat. Ofcourse, the density of a fluid makes a difference: the teddy bear would notneed as much help in a lake of molasses, since an equivalent volume of molasseswould weigh more and thus exert more buoyant force than water.Because the human body is itself mostl
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