Centrifugal force is a...

• A. gravity-like pull
• B. magnetic force
• C. a corollary of friction
• D. display of inertia

Answer: (D)

This item hinges on inertia and how it appears in a rotating frame. When an object moves in a circle, its body tends to keep moving in a straight line due to inertia. The path is curved by an inward force (the centripetal force) pointing toward the center. In a rotating reference frame, this outward tendency shows up as an apparent outward force—the centrifugal effect. So centrifugal force is best understood as a display of inertia: it arises from the object's resistance to change in direction as the path curves, not from gravity, magnetism, or friction. In an inertial frame, there is no outward force; the inward centripetal force is real, and the outward “force” is just a frame-dependent effect.