Question

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How do inertia and centripetal force combine to keep an object moving in circular motion?

Centripetal force acts toward the center of the circle to overcome inertia, which acts away from the center.
Inertia acts toward the center of the circle to overcome centripetal force, which acts away from the center.
Centripetal force acts toward the center of the circle, and inertia keeps the object moving forward.
Inertia acts toward the center of the circle, and centripetal force keeps the object moving forward.

Answer 1

Correct choice:
Centripetal force acts toward the center of the circle, and inertia keeps the object moving forward.

Why: inertia (mass) is the tendency of the object to keep moving in a straight line (tangentially). To make the object follow a circle its velocity direction must continually be changed; that requires a net inward force (the centripetal force). Mathematically the inward acceleration is ac = v^2/r, so the required inward force is Fc = m v^2 / r. There is no real outward “inertia force” in an inertial frame — an outward centrifugal force is only a fictitious force seen in a rotating reference frame.