No, really. I know there are some math-phobes and science-phobes out there. Take a deep breath. You can make it.
Newton's Third Law of Motion can be applied to the art of creating tension in your stories. His Third Law states that:
"For every action, there is an equal and opposite reaction."
When it comes to putting together a novel, short story, or other forms of prose, this law should be consistently applied throughout the unfolding plot. Tension is such an important factor to remember as you write. Without tension, the story of Dorothy Gale in The Wizard of Oz would just be the tale of a Kansas girl wandering aimlessly down a yellow brick road. Lord of the Rings would be a charming travel monologue.
However, too much tension can be just as detrimental. Lace every moment and every paragraph with tension, and both your characters--and your readers--will be nervous wrecks by the time you're done. Too much tension can also feel overly dramatic.
It is just as bad to start out with a large amount of tension, and then hit a sagging middle, and finally sputtering out completely by the end. It will leave a very nasty taste in a reader's mouth.
The best way to make sure your tension level is correct for the moment and scene, and to ensure that it is slowly building correctly toward a climatic end, apply Newton's Third Law.
Every action has a reaction, to summarize the law. If you introduce a particular fear in a character, ensure that the reaction to being faced with at some point is just as severe as her/his aversion to it. (And they should be faced with it, I might add. Though that's a topic for another post...)
If you have created an action that must be taken, ensure that the reaction to it matches up. Does your character detest, and even hate, the antagonist? Then the "pay-off" at the end, when one character defeats the other, should show a reaction to that hatred.
But, beware of being too dramatic. If you don't build in tension and "actions" that are wound throughout the story, your end "reaction" will fizzle.
Picture our space shuttle.
Little rockets + big shuttle = No liftoff
Big rockets + "small" shuttle = Explosive
Ensure that every action your characters take has a reaction within your narrative, that matches the original action in its intensity.
Intensity by Dean Koontz [thriller/mainstream]
Nightfall by Isaac Asimov and Robert Silverberg [science fiction]
Sword-Dancer series by Jennifer Roberson [fantasy]
The Taking by Dean Koontz [speculative fiction.]
(yes, I tributed him twice. The latter one is more subtle with the tension building. And the thriller is less subtle, for obvious reasons)