Which type of acceleration results from a simultaneous change in both speed and direction?

The type of acceleration that results from a simultaneous change in both speed and direction is angular acceleration. Angular acceleration refers to the rate at which an object changes its rotational speed and is applicable in scenarios where an object is moving along a curved path. In such cases, the object not only changes its speed but also its direction continuously, which is typical in circular or angular motion.

In this context, consider a vehicle taking a turn: it accelerates in the sense that it changes its linear speed as well as its direction of travel. Thus, whenever there's a change in the angle of orientation of the velocity vector along a curved path, angular acceleration is relevant.

Linear acceleration involves an increase or decrease in speed along a straight path but does not account for any change in direction. Radial acceleration, while related to motion in a circular path, specifically refers to the change in direction toward the center of curvature rather than speed. Negative G force refers to the sensation of being pushed down against the seat or surface, typically in decelerating scenarios or during rapid changes in pitch or roll, and is not directly related to the concept of acceleration combining speed and direction change.