tailieunhanh - Science of Everyday Things Vol. 2 - Physics Episode 10

Tham khảo tài liệu 'science of everyday things vol. 2 - physics episode 10', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | FREQUENCY If an object in harmonic motion has a frequency of 50 Hz its period is 1 50 of a second sec . Or if it has a period of 1 20 000 of a second sec that means it has a frequency of 20 000 Hz. REAL-LIFE A P P L I C AT IONS Grandfather Clocks and Metronomes One of the best-known varieties of pendulum plural pendula is a grandfather clock. Its invention was an indirect result of experiments with pendula by Galileo Galilei 1564-1642 work that influenced Dutch physicist and astronomer Christiaan Huygens 1629-1695 in the creation of the mechanical pendulum clock or grandfather clock as it is commonly known. The frequency of a pendulum a swing-like oscillator is the number of swings per minute. Its frequency is proportional to the square root of the downward acceleration due to gravity 32 ft or m sec2 divided by the length of the pendulum. This means that by adjusting the length of the pendulum on the clock one can change its frequency if the pendulum length is shortened the clock will run faster and if it is lengthened the clock will run more slowly. Another variety of pendulum this one dating to the early nineteenth century is a metronome an instrument that registers the tempo or speed of music. Consisting of a pendulum attached to a sliding weight with a fixed weight attached to the bottom end of the pendulum a metronome includes a number scale indicating the frequency that is the number of oscillations per minute. By moving the upper weight one can speed up or slow down the beat. Harmonìcs As noted earlier the volume of any sound is related to the amplitude of the sound waves. Frequency on the other hand determines the pitch or tone. Though there is no direct correlation between intensity and frequency in order for a person to hear a very low-frequency sound it must be above a certain decibel level. The range of audibility for the human ear is from 20 Hz to 20 000 Hz. The optimal range for hearing however is between 3 000 and 4 000 Hz. This .

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