Pressure is defined as force per unit area. It allows heavy loads to be supported inside car tires and causes feet to sink into soft ground. Increased pressure inside a pressure cooker allows food to cook more quickly at a high temperature. The pressure depends on both the force applied and the surface area, with greater pressure resulting from either a higher force or smaller surface area. Examples include skis distributing force over a large area to reduce pressure on snow, and sharp knives concentrating force into a small area to cut with high pressure.