Which force is primarily responsible for changing an object's direction as it moves in a circle, such as on a rollercoaster

• A. Gravitational force
• B. Frictional force
• C. Centripetal force
• D. Normal force

Answer: (C)

Moving in a circle requires a force directed toward the center of that circle, creating centripetal acceleration that continuously changes the direction of motion. On a rollercoaster, the track provides an inward push via the normal force, and gravity can also contribute some inward component depending on the position along the loop. The idea is that the net inward force toward the center is what continually redirects the car’s path from a straight line to a curved one. Centripetal force is the label given to that inward, center-seeking force (it’s not a separate new force by itself, but the result of the forces acting toward the center). Without this inward force, the car would just move straight due to inertia.