97 Go online to look up the difference between chemical, kinetic, and potential energy. This energy is partly converted into heat and deformation (e.g. bending of knees, compression of shoes, and ground impact). ONLINE RESOURCES The physics behind long jumps to neglect: trascurare to propel: spingere 180 SCIENCE AND PHYSICS JUMPS Jumping in sports relies on fundamental physics principles, including force, energy conversion, and projectile motion. Athletes generate force against the ground, propelling themselves into the air following a parabolic trajectory. uy Understanding physics behind jumps helps optimise sport performance. uy = 0 ux Force and Newton s laws Newton s second law: a jumper s acceleration depends on the force they apply to the ground and their body mass. A greater force or lower mass results in higher acceleration, leading to a more powerful jump. Newton s third law: when an athlete pushes down on the ground, the ground exerts an equal and opposite reaction force, propelling them upwards. Impulse and momentum Impulse measures how much momentum (i.e. the quantity of motion an object has) a jumper gains during take-off. A stronger and longer push against the ground increases impulse, generating more upward momentum and resulting in a higher jump. In long jump, for example, sprinting speed increases horizontal momentum, and a quick, explosive push at takeoff maximises impulse. In high jump, a longer ground contact time allows for greater impulse, increasing vertical momentum. The formula for impulse using momentum is: J = p = m . v, where: J = impulse (Newton-seconds) p = change in momentum (kg . m/s) m = mass of the athlete (kg) v = change in velocity (m/s) Projectile motion Parabolic trajectory: once the jumper leaves the ground, they move in a curved parabolic trajectory due to gravity. Vertical motion: gravity slows the ascent, stops it at the peak, and accelerates the descent. Horizontal motion: if a jump includes a forward motion (e.g. long jump), the horizontal velocity remains constant (neglecting air resistance). Energy conversion in jumps At take-off: the jumper s muscles contract to generate force. This force propels the jumper off the ground, converting chemical energy of muscle into kinetic energy (energy of motion). At peak height: as the jumper rises, kinetic energy (from upward motion) gradually converts into potential energy (the stored energy an object has due to its position). At this point, the vertical velocity becomes zero because all kinetic energy is converted into potential energy. During descent: gravity pulls the jumper back down. Upon landing, some kinetic energy is absorbed by the ground and body , while some may transfer into forward motion (e.g. in long jump).