Momentum transfer refers to the process by which momentum, a measure of motion, is exchanged between objects or systems. This can occur during collisions, where two bodies interact and their velocities change, resulting in a transfer of momentum from one to the other. The total momentum of the system remains constant, according to the law of conservation of momentum. In fluid dynamics, momentum transfer also occurs when fluids, such as air or water, move and interact with surfaces or other fluids. This can affect the behavior of objects in the fluid, such as airplanes or boats, as they experience forces due to the momentum exchange with the surrounding medium.