How small are the microorganisms that live on and in the human body? Microorganisms is smaller than a "???"

In a voltaic cell, electrons flow from the (positive/negative) to the (positive/negative) terminal.

Consider a system to be two train cars traveling toward each other. what is the total momentum of the system before the train cars collide?   kg • what must the total momentum of the system be after the train cars collide?   kg •  

Uppose we consider the system of the three capacitors as a single "equivalent" capacitor. given the charges of the three individual capacitors calculated in the previous part, find the total charge qtot for this equivalent capacitor. express your answer in terms of v and c.