Which of the following statements is false?
If the speed of a body is constant, then its velocity must be constant.
It is not necessary for velocity to be constant even if its speed is constant.
Speed a scalar quantity only has magnitude. Whereas velocity being a vector quantity has both magnitude and direction. i.e. the velocity of the object changes even when the direction of motion changes. So, if a body is changing its direction without changing its speed, then its velocity will change.
For example, a body in uniform circular motion has a constant speed, but its velocity changes as the direction of motion of the body changes.