Part 2: How a character’s internal change mirrors Newton’s Second Law

A brief recap

Last time, we talked about the external events surrounding our hero’s humble beginnings. Rather than starting out heroic, he or she tries to avoid the journey set before them.

  • During the reaping for The Hunger Games, the last thing Katniss wants is to volunteer to be a tribute.
  • In The Lord of the Rings, Frodo’s first reaction to Gandalf’s news about the ring is to give it away (to reject the journey).
  • Luke, too, in Star Wars: A New Hope, makes excuses for why he can’t go with Obi-wan.

They’re not looking for adventure, but their outward circumstances change in a way they can’t ignore. Outside force. Outward circumstances. Protagonist decisions leading to action. All these things fall within the realm of the plot—the physical journey: External changes. But the “outside force” triggers internal changes as well…

just like the debris expelled from Earth’s surface into orbit during the creation of the moon… (*WARNING: TANGENT ALERT!*)


Okay, so maybe an Earth particle blasted into space by a meteor doesn’t make for a great character…


But, I digress…

Internal Change (the realm of character arc)

In the first chapter, our protagonists are likely to be stuck in a rut—internally at least. They believe some lie, or they’re haunted by their past, or they’re hampered by besetting flaws that prevent them from fulfilling their dreams. Or maybe they’re hampered by a flaw because they believe a lie that was first stamped into their brains during some past traumatic event (i.e., their ghost or wound). The point is, most characters need to change (internally), but they can’t do it on their own.

Then along comes the “outside force” (e.g., meteor), and soon thereafter the protagonist’s decision launches him on a journey that takes the rest of the book to complete. Like the initial “outside force” that first sets your protagonist in motion, new external circumstances and events (all related to the central conflict) present new challenges for your hero to overcome. During the course of the journey, he struggles against various obstacles that force him to address his inner issues until he emerges, a changed man.


But how does all this relate to Newton’s second law?

F = ma, a = F/m

Newton’s Second Law is most familiar to people when it’s expressed as a formula. Force equals mass times acceleration

With a little rearrangement, this becomes: acceleration equals force divided by mass. In other words, there are two variables responsible for changes in the acceleration of a body: The Force (may it be with you) and the mass:

(1) Variations in the Force (↑F, ↑a … ↓F, ↓a)

In physical terms, the rate of change in velocity—i.e., acceleration—of a particular body is proportional to the total force acting on that body. Imagine shoving a shopping cart with a big vs. little oomph. (These are technical terms here, so you might want to jot some notes.) Obviously, the bigger oomph produces the greater acceleration.

In WriterSpeak, a character’s overall internal change will be proportional to the magnitude of difficulties he or she must overcome. In other words, the greater the forces acting on a character, the more he or she changes.


(2) Variations in the Mass (↑m, ↓a … ↓m, ↑a)

In physical terms, the greater the mass on which a given total force acts, the more sluggish the acceleration. That is to say, your shopping cart is harder to push once filled.

In WriterSpeak, the more sluggish or stubborn the character, the greater the forces needed to bring about a given change. In other words, more challenging trials will be required to reform Jack the Ripper than to convince Elizabeth Bennet to marry Mr. Darcy.

So, Newton’s second literary law speaks to the magnitude of a character’s internal change (or arc)…

The bottom line here is that every heroine needs impetus to overcome her issues. The more we want her to change, the more pressure we need to apply in the way of plot hurdles and difficult choices (i.e., internal and external conflict).


After all, characters are the most stubborn of people. They don’t learn from their mistakes the first time around. They aren’t self-enlightened individuals who spontaneously decide to become better people overnight. They scoff at their mentors, presuming they themselves know better—until struggle and hardship teach them otherwise. Only after they’ve experienced the full constriction of their flaws can they embrace the idea of change.

How about you? When you recognize flaws in yourself, do you find them easy to overcome? What about your characters? How is the magnitude of their arc proportional to the difficulties they have to face? Leave a comment below (and drop your email here) for a chance to win a 2500-word critique or an e-copy of K.M. Weiland’s book Creating Character Arcs.

Come back next week to peruse the next article in this series: Story Physics, Part 3: Action-Reaction in fiction as Newton’s Literary Third Law. Missed the first one? Check it out here: Part 1: How Newton’s First Law mimics character motivation.