93 Can you define friction? Search online if necessary. Gravity plays a key role in how speed is affected in different types of motion. In free fall, gravity causes objects to accelerate downward at a rate of 9.81 m/s². This results in an increase in speed as the object falls. ONLINE RESOURCES High-tech clothing to improve speed drag: resistenza gravel: ghiaia polished: levigato slipperiness: scivolosit slope: pendenza tile: piastrella uneven: iregolare HOW DIFFERENT CONDITIONS AFFECT SPEED There are several factors that can affect speed, including the force acting on the object, the mass of the object, the surface it is moving on, and the presence of friction or other resistive forces. Speed is also affected by environmental conditions such as air resistance, gravity, and weather. The physics behind these effects involves forces like frictional force, drag force, and gravitational force, which either increase or decrease movement efficiency. Understanding these principles helps explain why speed varies in different conditions. Indoor vs outdoor conditions Indoor environments: typically, indoor conditions have less air resistance and controlled surfaces (like smooth floors), allowing for faster movement. Outdoor environments: outdoor movement is affected by wind resistance (drag force), temperature variations, and uneven terrain, which can slow down an object. Wet / Icy surfaces: they cause low friction that can either increase speed (by reducing resistance) or make movement unstable and harder to control. Gravity and inclines (hills, slopes) Going downhill: objects accelerate due to gravity. Every percent gradient of decline will help by approximately 5 seconds per km. Going uphill: it requires extra force to overcome gravity, slowing down motion. Every percent gradient of incline will slow you by approximately 7.5-9 seconds per km. Weather conditions Rain/Snow: it increases slipperiness, reducing friction and control. Wind: it creates an additional drag force, which may oppose motion: Different types of ground/surface Smooth surfaces (e.g. tile, polished wood, asphalt): they cause less friction, allowing objects or people to move faster. Rough surfaces (e.g. grass, sand, gravel): they cause increased friction and energy loss, reducing speed. headwind (wind against motion) can decrease speed by increasing air resistance; but Uniform ball rebound creates consistent game play tailwind (wind from behind) can increase speed by providing extra force. Altitude and air density Force reduction reduces strain on lower extremities 174 SCIENCE AND PHYSICS Proper surface finish effect and vertical deformation minimise slipping and stumbling Higher altitudes (mountains): lower air density reduces drag, potentially increasing speed for fast-moving objects (e.g. sprinters); however, reduced oxygen levels can decrease human endurance. Lower altitudes (sea level): denser air increases resistance but provides more oxygen for endurance-based activities.