Inertia

Inertia is an object's resistance to changes in motion. Objects that are moving will resist speeding up, changing direction, or stopping, and objects that are stopped will resist moving. Objects with more mass will be more resistant to these changes. In SCUM, this translates to characters speeding up from a stop, slowing down after moving, and curved turns as opposed to sharp direction changes, with larger characters taking more time to do these.

Mechanics
When moving in SCUM, players have to be conscious of the fact that their movement carries forward. While this is most obvious when it comes to starting running, it applies to stopping as well. When stumbling upon Puppets, for instance, stopping too late can alert them, causing a swarming effect on your location. This can be somewhat negated turning to the side, but the best way to move is just to keep this in mind and move carefully. This is especially true in mountainous or hilly regions, as you can very quickly find yourself jumping off a cliff or high ledge due to inertia if you're not paying attention.

Players should note that the inertia factor can increase or decrease depending on player weight. The heavier a player is, the more inertia they carry, and vice versa.