what do you mean by a simple pendulum explain its structure and working with the help of a suitable diagram
Answers
A pendulum is a rod hanging vertically from its top end (or a weight called a bob hanging from a string) that swings from side to side due to the force of gravity. As Italian scientist Galileo Galilei (1564–1642) discovered, the clever thing about a pendulum is that it always takes the same amount of time to make one complete swing. In theory, the only thing that affects how fast a pendulum swings is its length and the strength of gravity.A pendulum works by converting energy back and forth, a bit like a rollercoaster ride. When the bob is highest (furthest from the ground), it has maximum stored energy (potential energy). As it accelerates down toward its lowest point (its midpoint, nearest the ground), this potential energy is converted into kinetic energy (energy of movement) and then, as the bob climbs up again, back to potential energy. So as the bob swings (oscillates) back and forth, it repeatedly switches its energy back and forth between potential and kinetic. Something that works this way is called a harmonic oscillatorand its movement is an example of simple harmonic motion, though we won't go into those things here.If there were no friction or drag (air resistance), a pendulum would keep on moving forever. In reality, each swing sees friction and drag steal a bit more energy from the pendulum and it gradually comes to a halt. But even as it slows down, it keeps time. It doesn't climb as far, but it covers the shorter distance more slowly—so it actually takes exactly the same time to swing. This handy ability (technically called isochronism, which just means "equal amounts of time") is what makes a pendulum so useful for timekeeping.
Galileo figured that out straight away and though he never actually managed to build a complete pendulum clock. he came quite close (here's a model of the 1642 pendulum clockhe was designing just before his death); it was left to another brilliant scientist, Dutchman Christiaan Huygens (1629–1695), to finish the job in the 1650s. (Read more about Huygens and his clocks and see a photo of the first Huygens pendulum clock of 1656.)Suppose you want to build a clock from scratch in the simplest way possible with the fewest number of parts. You could start with a dial and some hands and move them around the face with your finger, counting seconds to yourself and moving the hands accordingly. You move the second hand once a second, the minute hand once every 60 seconds, and the hour hand once every 60 minutes (3600 seconds). Some clock! That's going to get tedious quite quickly, so what about automating things? You could mount the hands on a little axle driven by what we'll call "timekeeping gears," so that the second hand automatically turns the minute hand at 1/60 of its speed, and the minute hand, likewise, turns the hour hand at 1/60 of its speed. Then all you have to do is count seconds, turn the second hand, and the rest of the job is done for you.
But, hang on, that's still pretty tedious. What we really need is some way of powering the hands automatically. You could wrap a piece of string around the axle and attach a weight to it. As the weight falls, it will pull the axle around, turn the second hand, and that will drive the rest of the clock. The only trouble is, the weight is going to fall really quickly and the second hand will whizz around too fast so the clock won't keep time. Okay, let's introduce another set of gears—we'll call them "power gears" (to avoid confusing them with the timekeeping gears)—that will take power from the falling weight and transform it so that, as the weight falls, the second hand advances exactly one position on the dial in one second. But that still won't work because the weight is going to accelerate as it goes down, like any falling object. In other words, the clock is going to get faster and faster until the weight hits the ground with a smack!
What we need to add is a mechanism that regulates how fast the weight can fall, allowing the whole timekeeping mechanism to advance so the second hand moves one second on the dial (and only one second) in a time of one second. That's what the pendulum does. As it swings from side to side, it rocks a lever called an escapement that locks and then unlocks the part of the mechanism driven by the falling weight. (Think of it this way: the mechanism is locked and the escapement releases it so it can move—in other words, lets it escape—once per second.) It's this repeated locking and unlocking that makes the tick-tock sound you can hear. Since (in theory, at least) a pendulum of a certain length always takes the same amount of time to swing back and forth, the pendulum is what keeps the clock to time. The escapement mechanism that the pendulum regulates also (cleverly) keeps it moving back and forth by repeatedly giving it a slight nudge—an extra injection of energy to counteract friction and drag.
Simple Pendulum: an ideal pendulum consisting of a point mass suspended by a weightless inextensible perfectly flexible thread and free to vibrate without friction —distinguished from physical pendulum
Exploring the simple pendulum a bit further, we can discover the conditions under which it performs simple harmonic motion, and we can derive an interesting expression for its period.
