When swinging a ball on a string, the existence of a normal force depends on the observer's perspective. An outside observer sees no normal force, as tension in the string accounts for the centripetal motion. However, from the ball's perspective, a pseudoforce appears to act outward, but this does not constitute a normal force since it lacks contact with a surface. The discussion emphasizes that normal forces require a physical surface for contact, and the concept of pseudoforces is relevant in non-inertial reference frames. Understanding these principles clarifies the dynamics of centripetal acceleration in different frames of reference.