Here's why:
* Centripetal Force: This force is always directed towards the center of the circular path and is necessary to keep an object moving in a circle. Without it, the runner would continue in a straight line (Newton's First Law).
* Friction's Role: The runner pushes against the track with their feet, and the track pushes back. This force of friction acts as the centripetal force. It's the force that prevents the runner from sliding outward as they round the curve.
Factors Affecting Friction:
* Track Surface: A rougher surface provides more friction.
* Runner's Shoes: Spikes on running shoes increase friction.
* Speed: Higher speeds require more friction to maintain a circular path.
Note: Other forces like air resistance can also contribute to the centripetal force, but friction between the shoes and the track is the primary source.
