Pendulum is a very down-to-earth guy


So yesterday my author discussed about two very important systems of classical mechanics. Actually this guy seems to be obsessed with these two systems.

What he was talking about? A harmonic oscillator and a pendulum. An HO is different from a pendulum. That's because gravity plays no role in one but a major role in the other. Why is that so? Take out the spring from your pen and place it on the table. Hold it from behind so that it stays in position. Now push it inward. No need to hold on. Just release. What do you see? Did the spring bounce back? Ah yes, but does it bounce back to its original position? No. It moved beyond its position, right? And then we observe this to and fro motion. Well that won't last long since we have too many retarding forces in the real world. But that's not what we are worried about now. What is the role of gravity here? Did gravity play a role in bringing the spring back to its original position? No, it didn't.

But that's not the case with a pendulum. A pendulum is something whose whole existence and importance is due to gravity. Imagine you place a pendulum on a table, attach it to a thin rod, drag it to the left and release it. What do you see? We see the bob moving towards the right along with the rigid rod, right? No, you didn't. The bob remained where it was. Why was that so? Because the pendulum was not hanging but lying on a horizontal surface. The potential which should have driven it the original position doesn't exist. How will that potential come to life? We hang it upside down.

Hence the proof, the life of a pendulum revolves around gravity.


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