# Inertia

Consider, if you will, Newton’s Laws of Motion. Here you go:

Law 1: Every object persists in a state of rest unless it is compelled to change that state by forces impressed on it.

Law 2: The acceleration of an object is tied directly to the power of the force acting on it, and also to the object’s mass. Put another way– the heavier the object, the greater the force you will need to move it.

Law 3: For every action, there is an equal and opposite reaction.

Picture a swimmer ready to turn. She places her feet against the wall and pushes. No matter how strong she is, the wall is stronger. Or, rather, the force the wall exerts on the swimmer is stronger than the force the swimmer can possibly exert against the wall. She is propelled forward through the water. The stronger the swimmer is, the more force she can exert against the wall. The more force she exerts– the harder she pushes– the faster she will get away from the wall. The faster she can leave it behind.

Without the wall, she cannot change direction. She has to hit the wall first to start moving away from it. So, the swimmer has to plan for contact. If she simply collides with the wall, exerting only the force of the inertia she had built up from the swim, she will drift aimlessly in the water for a few feet. And then, unless she acts against the water, she will sink.

But if she plans the collision carefully, tucks her feet underneath her body, and pushes– HARD– against the wall that is designed to stop her, she will find herself slipping away from it. Again– not for long– because the water exerts a force too, called drag. The swimmer has to keep moving, using her hands and legs and a lot of energy, to push against the water.