A uranium-235 atom is moving forwards in a reactor with a velocity of 6.2 x 10' ms" when it undergoes spontaneous fission into a krypton (Kr) atom and a Barium (Ba) atom. The Kr atom is ejected backwards at a velocity of 3.3 x 10 ms" whilst the Ba atom is projected forwards (atomic masses are: U = 235 U, Kr = 95 u and Ba = 140 u) 6.2 x 105 ms 3.3 x 105 ms V U-235 Kr-95 Ba-140 The velocity of the barium atom after fission has occurred is about: A. 1.9 x 10' ms-1 B. 8.7 x 10' ms C. 2.6 x 10' ms D. 3.3 x 10' ms"