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	<title>Physics Club &#8211; Sidspark</title>
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	<description>Cheer for the Diversity of Human Beings</description>
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		<title>How Differential Equations Describe the Physics World &#8211; Why Carrying Pole Has to Be Floppy Before It Helps You</title>
		<link>https://sidspark.site/2026/08/06/how-differential-equations-describe-the-physics-world-why-carrying-pole-has-to-be-floppy-before-it-helps-you/</link>
					<comments>https://sidspark.site/2026/08/06/how-differential-equations-describe-the-physics-world-why-carrying-pole-has-to-be-floppy-before-it-helps-you/#respond</comments>
		
		<dc:creator><![CDATA[Ender]]></dc:creator>
		<pubDate>Thu, 06 Aug 2026 12:36:12 +0000</pubDate>
				<category><![CDATA[Physics Club]]></category>
		<guid isPermaLink="false">https://sidspark.site/?p=264</guid>

					<description><![CDATA[Ask anyone who grew up carrying things in the Chinese countryside and you will get the same sentence, delivered with total confidence and zero elaboration: a bamboo carrying pole is easier on you than a rigid one. 省力, in the one word they always use — not &#8220;more comfortable&#8221;, n &#8230;]]></description>
		
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			<slash:comments>0</slash:comments>
		
		
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		<title>Bertrand&#8217;s Theorem: Only Two Forces in the Universe Let Orbits Close</title>
		<link>https://sidspark.site/2026/07/08/bertrands-theorem-only-two-forces-in-the-universe-let-orbits-close/</link>
					<comments>https://sidspark.site/2026/07/08/bertrands-theorem-only-two-forces-in-the-universe-let-orbits-close/#respond</comments>
		
		<dc:creator><![CDATA[Ender]]></dc:creator>
		<pubDate>Wed, 08 Jul 2026 13:50:52 +0000</pubDate>
				<category><![CDATA[Physics Club]]></category>
		<guid isPermaLink="false">https://sidspark.site/?p=262</guid>

					<description><![CDATA[Two posts ago I argued that the exponent 2 in $1/r^2$ is doing far more work than it looks like it&#8217;s doing — it hides the dimensionality of space, and it&#8217;s the whole reason a spherical shell is hollow. Last post I turned the crank on the differential equation and got a conic sec &#8230;]]></description>
		
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			<slash:comments>0</slash:comments>
		
		
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		<title>How Differential Equations Describe the Physics World &#8211; Why Planetary Orbits are Ellipses</title>
		<link>https://sidspark.site/2026/05/15/how-differential-equations-describe-the-physics-world/</link>
					<comments>https://sidspark.site/2026/05/15/how-differential-equations-describe-the-physics-world/#respond</comments>
		
		<dc:creator><![CDATA[Ender]]></dc:creator>
		<pubDate>Fri, 15 May 2026 11:01:07 +0000</pubDate>
				<category><![CDATA[Physics Club]]></category>
		<guid isPermaLink="false">https://sidspark.site/?p=221</guid>

					<description><![CDATA[In a previous article I talked about how to use only one simple spring force to set up a differential equation and solve it to give the dynamics of SHM, which is a typical projection of uniform circular motion. Forces that follow the Hook&#8217;s Law seem to be very special in real world. T &#8230;]]></description>
		
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			<slash:comments>0</slash:comments>
		
		
			</item>
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		<title>Playing Pool with Pi &#8211; Part 3 &#8211; What Happens to the π When the Blocks Aren&#8217;t Perfectly Bouncy?</title>
		<link>https://sidspark.site/2026/04/24/playing-pool-with-pi-part-3-what-happens-to-the-%cf%80-when-the-blocks-arent-perfectly-bouncy/</link>
					<comments>https://sidspark.site/2026/04/24/playing-pool-with-pi-part-3-what-happens-to-the-%cf%80-when-the-blocks-arent-perfectly-bouncy/#respond</comments>
		
		<dc:creator><![CDATA[Ender]]></dc:creator>
		<pubDate>Fri, 24 Apr 2026 11:34:33 +0000</pubDate>
				<category><![CDATA[Physics Club]]></category>
		<guid isPermaLink="false">https://sidspark.site/?p=256</guid>

					<description><![CDATA[Last time I wrote about the block collision puzzle: heavy block, light block, wall, no friction, perfectly elastic collisions, and the number of clacks turns out to be the digits of π. Perfectly elastic. That assumption did a lot of work. Real collisions lose energy. Steel on steel gives yo &#8230;]]></description>
		
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			<slash:comments>0</slash:comments>
		
		
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		<title>The Privilege of the Inverse Square: Two Proofs of the Shell Theorem</title>
		<link>https://sidspark.site/2026/03/22/the-privilege-of-the-inverse-square-two-proofs-of-the-shell-theorem/</link>
					<comments>https://sidspark.site/2026/03/22/the-privilege-of-the-inverse-square-two-proofs-of-the-shell-theorem/#respond</comments>
		
		<dc:creator><![CDATA[Ender]]></dc:creator>
		<pubDate>Sun, 22 Mar 2026 12:52:19 +0000</pubDate>
				<category><![CDATA[Physics Club]]></category>
		<guid isPermaLink="false">https://sidspark.site/?p=257</guid>

					<description><![CDATA[In the last post I borrowed a point from Feynman: the mathematical form of a law carries far more physics than the sentence it seems to be saying. This post is a worked example. Nominally we are proving the shell theorem. What we are really after is a more pointed question — why is gravity  &#8230;]]></description>
		
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			<slash:comments>0</slash:comments>
		
		
			</item>
		<item>
		<title>The Unreasonable Effectiveness of Mathematics in the Natural Sciences &#8212; Lecture share</title>
		<link>https://sidspark.site/2026/02/22/the-unreasonable-effectiveness-of-mathematics-in-the-natural-sciences-lecture-share/</link>
					<comments>https://sidspark.site/2026/02/22/the-unreasonable-effectiveness-of-mathematics-in-the-natural-sciences-lecture-share/#respond</comments>
		
		<dc:creator><![CDATA[Ender]]></dc:creator>
		<pubDate>Sun, 22 Feb 2026 13:06:09 +0000</pubDate>
				<category><![CDATA[Physics Club]]></category>
		<guid isPermaLink="false">https://sidspark.site/?p=233</guid>

					<description><![CDATA[Today when reading&#160;useless&#160;articles on&#160;知乎,&#160;I found a pretty interesting problem discussing the inherent relationship between physics and mathematics. It really echoes my thoughts recently. Personally, I realized this magical connection when I started to learn physics&#038;n &#8230;]]></description>
		
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			<slash:comments>0</slash:comments>
		
		
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		<title>Playing Pool with Pi &#8211; Part 2 &#8211; Two Blocks, One Wall, and a Very Silly Way to Compute π</title>
		<link>https://sidspark.site/2026/01/27/playing-pool-with-pi-part-2-two-blocks-one-wall-and-a-very-silly-way-to-compute-%cf%80/</link>
					<comments>https://sidspark.site/2026/01/27/playing-pool-with-pi-part-2-two-blocks-one-wall-and-a-very-silly-way-to-compute-%cf%80/#respond</comments>
		
		<dc:creator><![CDATA[Ender]]></dc:creator>
		<pubDate>Tue, 27 Jan 2026 11:56:02 +0000</pubDate>
				<category><![CDATA[Physics Club]]></category>
		<guid isPermaLink="false">https://sidspark.site/?p=254</guid>

					<description><![CDATA[I want to tell you about the strangest place I have ever seen π show up. Here&#8217;s the setup. You have a frictionless floor. There&#8217;s a wall on the left. Next to the wall sits a small block of mass $m$, just sitting there. Coming in from the right is a big block of mass $M$, sliding &#8230;]]></description>
		
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			<slash:comments>0</slash:comments>
		
		
			</item>
		<item>
		<title>Wanting a Mechanism Is Wanting a Story</title>
		<link>https://sidspark.site/2026/01/20/wanting-a-mechanism-is-wanting-a-story/</link>
					<comments>https://sidspark.site/2026/01/20/wanting-a-mechanism-is-wanting-a-story/#respond</comments>
		
		<dc:creator><![CDATA[Ender]]></dc:creator>
		<pubDate>Tue, 20 Jan 2026 12:31:39 +0000</pubDate>
				<category><![CDATA[Physics Club]]></category>
		<guid isPermaLink="false">https://sidspark.site/?p=255</guid>

					<description><![CDATA[On Feynman&#8217;s second lecture in &#8220;The Character of Physical Law&#8221; Popular physics books rarely fail by being too hard. They fail by being too easy. You understand every sentence and none of the whole. Finish a book about gravity and what you&#8217;re holding is a row of indep &#8230;]]></description>
		
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			<slash:comments>0</slash:comments>
		
		
			</item>
		<item>
		<title>Playing Pool with Pi &#8212; Part 1 &#8212; Why can Simple Harmonic Motion be Described by Circular Motion</title>
		<link>https://sidspark.site/2025/12/22/playing-pool-with-pi-part-1-why-can-simple-harmonic-motion-be-described-by-circular-motion/</link>
					<comments>https://sidspark.site/2025/12/22/playing-pool-with-pi-part-1-why-can-simple-harmonic-motion-be-described-by-circular-motion/#comments</comments>
		
		<dc:creator><![CDATA[Ender]]></dc:creator>
		<pubDate>Mon, 22 Dec 2025 12:35:51 +0000</pubDate>
				<category><![CDATA[Physics Club]]></category>
		<guid isPermaLink="false">https://sidspark.site/?p=137</guid>

					<description><![CDATA[Introduction Recently, when we studied oscillation or SHM &#8212;- fundamentals of waves and periodic motions &#8212;- Birdy(鸟哥) asked me a question that &#8220;seemed&#8221; to be so obvious: why the equation of oscillations are derived from the circular motion? Here are some explanation &#8230;]]></description>
		
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			<slash:comments>1</slash:comments>
		
		
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