1. The problem statement, all variables and given/known data An electron has a speed of v = 0.14c. At what speed will a proton have a momentum equal to that of the electron? 2. Relevant equations p=mv 3. The attempt at a solution MeVe = MpVp where p=proton and e=electron so: MeVe/Mp=Vp Me = 9.109 X 10^-31 kg Mp = 1.672 X 10^-27 kg Plugging this information in gives me an answer of 22873.91 m/s but the correct answer is 23139.3 m/s. What am I doing wrong? Thanks in advance for any help!