Which of the following strikes is NOT used to stop a subject in forward momentum?

The side kick is not typically employed to stop a subject in forward momentum because it is primarily a striking technique aimed at creating distance or sending an opponent away from the user rather than halting forward motion. The side kick is delivered sideways and is effective for striking an opponent at an angle, which can push them back or to the side according to the force and angle applied.

In contrast, the palm heel strike, straight punch, and roundhouse kick are designed to deliver force directly onto the target in a manner that can impede or disrupt a subject's movement toward an officer. These techniques utilize forward motion and line of sight to create maximum stopping power against a subject's advance. Therefore, while these strikes can interrupt momentum effectively, the side kick does not serve the same purpose in the context of directly stopping forward movement.