Final answer:
The question deals with the final speed of muons after a relativistic collision, requiring knowledge of relativistic physics to solve, but lacks enough information to provide a specific answer.
Step-by-step explanation:
The question presented is concerning the final speed of two muons after a head-on collision, with one muon traveling at 50% the speed of light and the other at 70% the speed of light. To address this question accurately, one must use the principles of relativistic physics given that the speeds involved are significant fractions of the speed of light. However, without the rest mass of the muons and additional information about the nature of the collision (elastic or inelastic), it is not possible to provide a precise answer. Typically, if momentum and energy are conserved, the final velocities would depend on these factors. In relativistic collisions, the velocities can't be simply added together; relativistic velocity addition formulas would need to be used.