A Newton-second is a unit of measurement in the International System of Units (SI) that combines force and time. It is defined as the amount of force, measured in Newtons, applied to an object for one second. This unit is often used in physics to describe the momentum of an object, which is the product of its mass and velocity. In practical terms, one Newton-second represents the change in momentum of an object when a force of one Newton is applied for one second. This concept is important in understanding how forces affect the motion of objects, as described by Isaac Newton's laws of motion.