Instead of a massless string running from the pivot to the mass, there's a massive steel rod that extends a little bit beyond the ideal starting and ending points. Instead of an infinitesimally small mass at the end, there's a finite (but concentrated) lump of material. The reason for the discrepancy is that the pendulum of the Great Clock is a physical pendulum. In part a ii we assumed the pendulum would be used in a working clock - one designed to match the cultural definitions of a second, minute, hour, and day. In part a i we assumed the pendulum was a simple pendulum - one with all the mass concentrated at a point connected to its pivot by a massless, inextensible string. That way an engineer could design a counting mechanism such that the hands would cycle a convenient number of times for every rotation - 900 cycles for the minute hand and 10,800 cycles for the hour hand. The period of the Great Clock's pendulum is probably 4 seconds instead of the crazy decimal number we just calculated. What is the period of the Great Clock's pendulum?Ĭalculate the period of a simple pendulum whose length is 4.4 m in London where the local gravity is 9.81 m/s 2. By what amount did the important characteristic of the pendulum change when a single penny was added near the pivot? Now for a mathematically difficult question.Why does this method really work that is, what does adding pennies near the top of the pendulum change about the pendulum?.What error did the reporter make in his explanation? "When the clock is found to be gaining or losing time, the weight of the pendulum is fractionally adjusted by the addition or removal of an old-fashioned penny piece." While this statement is true, it does not explain how adding a penny affects the operation of the pendulum. Read this quote from a 2007 article in the Daily Mail.The pennies are not added to the pendulum bob (it's moving too fast for the pennies to stay on), but are instead placed on a small platform not far from the point of suspension. Adding one penny causes the clock to gain two-fifths of a second in 24 hours. Pennies are used to regulate the clock mechanism (pre-decimal pennies with the head of Edward VII).What is the cause of the discrepancy between your answers to parts i and ii?.What is the most sensible value for the period of this pendulum? The period you just calculated would not be appropriate for a clock of this stature.Begin by calculating the period of a simple pendulum whose length is 4.4 m.What is the period of the Great Clock's pendulum? This is not a straightforward problem. The heart of the timekeeping mechanism is a 310 kg, 4.4 m long steel and zinc pendulum.(The House of Commons chamber was destroyed in this attack.) It continued to operate even after sustaining damage in a German air raid in 1941. During World War II, the Great Clock was a symbol of British resiliency. Many home doorbells and school bells are programmed to play the Westminster Quarters - the four permutations of four notes that announce the quarter hours. The 12×12×96 meter tower that houses the Great Clock is the iconic symbol of the British Parliament. It is sometimes called "Big Ben", but strictly speaking that is the name of the 13.7 tonne Great Bell. The Great Clock of Westminster is undoubtedly the world's most famous clock. Pendulum clocks really need to be designed for a location.
That's a gain of 3084 s every 30 days - also close to an hour (51:24). That's a loss of 3524 s every 30 days - nearly an hour (58:44).ĭivide this into the number of seconds in 30 days. Half of this is what determines the amount of time lost when this pendulum is used as a time keeping device in its new location.ĭividing this time into the number of seconds in 30 days gives us the number of seconds counted by our pendulum in its new location. This part of the question doesn't require it, but we'll need it as a reference for the next two parts.īack to the original equation. Let's calculate the number of seconds in 30 days. Since gravity varies with location, however, this standard could only be set by building a pendulum at a location where gravity was exactly equal to the standard value - something that is effectively impossible.
In the late 17th century, the the length of a seconds pendulum was proposed as a potential unit definition. (Keep every digit your calculator gives you. The period of a simple pendulum is described by this equation.
0 kommentar(er)
