F=ma 2012 Problem 4

A particle at rest explodes into three particles of equal mass in the absence of external forces. Two particles emerge at a right angle to each other with equal speed v. What is the speed of the third particle?

Answer Choices
A. v
B. \sqrt{2} v
C. 2 v
D. 2 \sqrt{2} v
E. The third particle can have a range of different speeds.