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The length of the key chain pocket watches is the thread, which in practice represents the distance between the point of suspension and the center of the small little sphere, or center of gravity of it. Its period of oscillation is the time taken for the pendulum to complete one full cycle of motion, ie between the departure of an extreme position and return to it. The pocket watches obey the following laws established by Galileo: • Law of isochronisms: At one time the pendulum oscillation amplitude depends, in fact, if measured with a stopwatch clock time when the oscillation amplitude is small, 50 or 60 and then when it is higher, 100 or 150, it is found that the same result. • Law of the masses: The time of oscillation depends on the pendulum mass. In fact, if you take two pendulums of equal length, an iron and a wood, you'll notice it takes to rock the same time. • Law of the lengths: The time of oscillation of a pendulum is proportional to the square root of length. If the length of a pendulum is 4 times larger, the time doubles, as 2 is the square root of 4. The pocket watches models are hard to ignore. They are majestic in so many ways! You cannot forget to look onto vintage models. But if you like modern items, you can find them, too- there are several on the market. The best part is, these are not so expensive! They are used for measuring time, clocks, to determine the acceleration of gravity, using the formula of the pendulum which states: - Where T is the period of oscillation of the pendulum, l its length, g is the acceleration of gravity, and p (Greek letter that corresponds to our p) the immeasurable value of the ratio of circumference to diameter, which is approximately equal to 3.14. - This system is also used to check the rotation of the earth, the French physicist Leon Foucault (1819? 1898) found, in 1851, the Earth's rotation with huge pendulum suspended from the dome of the Pantheon in Paris. Note that the period of oscillation of a pendulum, metal, and length, are affected by temperature variations because it causes expansion or shrinkage of the rod that holds the weight. This is corrected using expandable metals, or by using different metal rods arranged such that length variations compensate each other and therefore do not alter the length of the pendulum. Truth is, this method is applied on every retro pocket watches.
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