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From cars to smartphones, all the technology we rely on is engineered using physics. You don’t need to know science to use them. But a well-rounded person must understand at least some basic concepts – some music, art, history and economics. Robert Heinlein said it all Enough time for love:
“One must be able to change a diaper, plan an invasion, butcher a pig, steer a ship, design a building, write a sonnet, balance accounts, build a wall, set a bone, console the dying, take orders. give orders, cooperate, act alone, solve equations, analyze a new problem, throw manure, program a computer, cook delicious food, fight effectively, die bravely. Specialization is for insects.”
So here are my top five physics equations you need to know so you don’t become an insect.
1. Newton’s Second Law
I’m sure you’ve seen it before – it’s over 300 years old and famous for science memes and t-shirts. It says that the net force on an object is equal to its mass (m) times acceleration (a). But what does that really mean? It’s all about interactions – like when you kick a soccer ball or drop a water bottle.
Newton’s second law says that we can describe these interactions with the concept of “force”. So what do the forces do? A net force acting on an object changes the object’s motion. But wait! There is much more to this seemingly simple equation.
Look at those arrows F and a? This indicates variables that are vectors, meaning they contain more than one piece of data. For example, if someone asked you to “socially distance” yourself by 1 meter, where would you end up? Who knows? You can go 1 meter east or west or 39 degrees north. Distance itself is not the whole story; you must also determine the direction. This is true for both forces and acceleration. Other quantities (such as mass or temperature) have no direction. We call this scalar values.
Newton’s second law is very useful, but it is strange that people do not believe in it. A common misconception is that a constant force causes an object to move at a constant speed. This equation means that if you push an object with a constant force, it will continue to accelerate.
