Hecta is the prefix meaning 100 times; Kilo means 1000 times; Deca is one tenth; and Centi is one hundredth. In this case, the smallest and most suitable for measuring small objects would be Centi.
No work is required to maintain an object at a constant speed with no change in direction. Work is only done when an object is accelerated, or moved some distance in the direction of the net force applied.