Two particles are moving along the x axis. Particle 1 has a mass m1 and a velocity v1 = +3.5 m/s. Particle 2 has a mass m2 and a velocity v2 = -6.3 m/s. The velocity of the center of mass of these two particles is zero. In other words, the center of mass of the particles remains stationary, even though each particle is moving. Find the ratio m1/m2 of the masses of the particles.