Which circumstance ensures an object remains in uniform circular motion?

In uniform circular motion, an object travels in a circular path at a constant speed. For this motion to occur, a force must act upon the object to continually change its direction, as velocity is defined as both speed and direction. The key requirement is that there be a net inward force directed towards the center of the circular path. This net inward force is known as centripetal force, and it is necessary to keep the object moving in that curved trajectory rather than continuing in a straight line, as would happen if no net force acted on it.

For instance, when a car turns around a curve, the friction between the tires and the road provides the inward force needed to keep the car on its curved path. Without this inward force, the car would not be able to follow the curve and instead would travel off in a straight line at the tangent to the curve.

Thus, the circumstance that ensures an object remains in uniform circular motion is the presence of a net inward force acting towards the center of the circle, making this choice the correct one.