What is drag?

Drag is a force that acts on objects moving through a fluid, such as air or water, and opposes their motion. It is caused by the friction and pressure differences that occur between the object and the fluid. The amount of drag depends on the shape, size, and speed of the object as well as the properties of the fluid. A streamlined shape usually produces less drag than a flat or irregular shape. Drag is important in many fields, including aerodynamics, hydrodynamics, and sports such as cycling and skiing. Reducing drag can improve efficiency and performance, and this is often achieved by using aerodynamic design, coatings, and materials.