When an object starts moving at a constant speed and then stops, its velocity undergoes a change. Velocity is a vector quantity that describes both the speed and direction of an object's motion.
Initially, when the object starts moving at a constant speed, its velocity increases in the direction of its motion. As time passes, the object maintains the same speed and direction, resulting in a constant velocity.
However, when the object comes to a stop, its velocity changes. Since velocity accounts for both speed and direction, stopping implies a change in either one or both of these aspects. In this case, the object's speed decreases gradually until it reaches zero, while its direction may remain unchanged. The process of slowing down and eventually coming to a stop is referred to as deceleration or negative acceleration.
It's important to note that an object's velocity changes even if it maintains a constant speed while stopping. This is because velocity considers both the magnitude (speed) and direction of motion. When an object's speed decreases to zero, its velocity changes from a non-zero value to zero.