1. The problem statement, all variables and given/known data A proton is fired from far away toward the nucleus of an iron atom. Iron is the element number 26 and the diameter of the nucleus is 9.0fm. What initial speed does the proton need to just reach the surface of the nucleus? Assume the nucleus remains at rest. 2. Relevant equations Conservation of energy which would get reduced to Ki=Uf U=kq1q2/r kinematic equation K = 1/2 m v^2 Do some thing with the element number 26... has 26 protons so make a field????? 3. The attempt at a solution Oh gosh. K this is completely wrong but ill just throw it out there for kicks. Ki=Uf Since i dont knwo what r is since its sperical and that confuses me.... ill guess you use the distance on the surface of the nucleus? 1/2mv^2 = kq1q2/r 1/2 (1.67E-27) v^2 = 9E9 (1.6E-19) (26*1.6E-19) / 4.5fm v = 350192 the answer is 3.99E7 Thank you!!!!