CBSE Class 9 Answered

Velocity has two components, speed and direction.  Speed can bemeasured in whatever units you like, say miles per hour.  Direction is definedby the person doing the measurement.  So, if I define one direction to be positive I will have a positive velocity when travelling in thatdirection.  I will have a negative velocity when travelling in the opposite direction

you cannot have a negative speed many physical quantities, BY DEFINITION, cannot be negative some examples: speed, mass, measurements of size, the direction of time