99 What does a Newton correspond to? Which of Newton s laws is about inertia? The centrifugal effect is the apparent outward force that a moving object feels when travelling in a curved path. It is not a real force but rather a result of inertia which causes objects to resist changes in motion and continue moving in a straight line. banked: inclinato to glide: scivolare inwards: verso l interno lean: inclinato outward: verso l esterno slipping: scivolamento tilt: inclinazione BENDS When athletes move around bends at speed, for example in track running, cycling, skiing, or speed skating, they experience forces that affect their motion. Unlike moving in a straight line, moving along a curve requires a continuous change in direction and the involvement of special forces that come from the interaction between their equipment (i.e. skis, shoes, skates, etc.) and the surface they are moving on. Let s see what the forces involved are. Centripetal force To move along a curved path, athletes must constantly change direction, so they are subjected to a force pulling them inwards toward the centre of the curve, known as centripetal force (expressed in Newton ). Without this force, the athletes would move in a straight line due to inertia . In sports like running, cycling, or speed skating, friction between the ground and the athlete s feet (or wheels/skates) provides this inward force, whose formula is: mv 2 Fc = r where: m = mass of the athlete (kg) v = speed (m/s) r = radius of the curve (m). Lean angle Athletes lean inwards towards the centre of the curve to counteract the outward pull (centrifugal effect ) and maintain balance. The lean angle depends on speed (the faster an athlete moves, the greater the force needed to keep them on the curve, requiring a steeper lean) and the curve radius: on tighter curves, more force is needed to stay on track, increasing the required lean angle. The formula of the lean angle is: v2 tan ( ) = rg where: = lean angle (degrees) v = speed of the athlete (m/s) r = radius of the curve (m) g = acceleration due to gravity (9.81 m/s²). Banked tracks In sports like cycling and track running, curved tracks are often banked to help athletes maintain speed and stability while turning. Without banking, they would have to rely entirely on friction between their feet (or wheels) and the ground to generate centripetal force, which keeps them moving in a curve. However, at high speeds, friction alone may not be enough, increasing the risk of slipping outwards. The steeper the banking angle, the greater the support, enabling higher speeds while minimising energy loss. 182 SCIENCE AND PHYSICS