Merge pull request #766 from nature-of-code/notion-update-docs

[Notion] Update docs

content/02_forces.html

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 <p>In the final example of Chapter 1, I demonstrated how to calculate a dynamic acceleration based on a vector pointing from a circle on the canvas to the mouse position. The resulting motion resembled a magnetic attraction between shape and mouse, as if a <em>force</em> was pulling the circle in toward the mouse. In this chapter, I’ll detail the concept of a force and its relationship to acceleration. The goal, by the end of this chapter, is to build a simple physics engine and understand how objects move around a canvas, responding to a variety of environmental forces.</p>
 <p>A <strong>physics engine </strong>is a computer program (or code library) that simulates the behavior of objects in a physical environment. With a p5.js sketch, the objects are 2D shapes, and the environment is a rectangular canvas. Physics engines can be developed to be highly precise (requiring high-performance computing) or real time (using simple and fast algorithms). This chapter focuses on building a rudimentary physics engine, with an emphasis on speed and ease of understanding.</p>
-<p>(test change)</p>
 <h2 id="forces-and-newtons-laws-of-motion">Forces and Newton’s Laws of Motion</h2>
 <p>Let’s begin by taking a conceptual look at what it means to be a force in the real world. Just like the word <em>vector</em>, the term <em>force</em> can have a variety of meanings. It can indicate a powerful physical intensity, as in “They pushed the boulder with great force,” or a powerful influence, as in “They’re a force to be reckoned with!” The definition of <strong>force</strong> that I’m interested in for this chapter is more formal and comes from Sir Isaac Newton’s three laws of motion:</p>
 <p><span class="highlight">A force is a vector that causes an object with mass to accelerate.</span></p>