試題詳解

13. A proton is projected toward a fixed nucleus of charge +Ze with velocity V₀ . Initially the two particles are very far apart.When the proton is at a distance R from the nucleus, its velocity has decreased to1/2 V₀ .How far from the nucleus will the proton be when its velocity has dropped to1/4 V₀? 
(A) 1/16 R
(B) 1/4 R
(C) 1/2 R
(D) 4/5 R
(E) 6/7 R