An observer that stands still as the electron moves by him, will observe

Ke reqd to move from 0 to 50 will be proportional to 50x50 or 2500. this is equal to w.  to change vel from 50 to 150 you need energy prop to 22500 - 2500 = 20,000. this corresponds to 8w.  best answer is a) . work reqd is prop to velocity squared. 

Th answer is 3200 m/s

Answerthe number of protons in an atom is its atomic number