試題詳解

23. An antiproton has the same rest mass as a proton which is created in the reaction p+p→p+p+p+. If two initial protons are moving with equal speeds in opposite directions and continue to exist after a head-on collision that also produces an extra pair of p-. If all four particles are at rest after the collision, what is the initial speed of the protons in their center-of-momentum frame? (Hint: Energy is conserved in the collision.)
(A) 1.2c
(B)
(C)
(D) 0.6c

(E) (2-)c