Now Jed and Kadia tackle a homework problem: An object of mass m1 = 15 kg and velocity v1 = 1.5 m/s crashes into another object of mass m2 = 6 kg and velocity v2 = −15.5 m/s. The two particles stick together as a result of the collision. Because no external forces are acting, the collision does not change the total momentum of the system of two particles, so the principle of conservation of linear momentum applies. m1v1i + m2v2i = (m1 + m2)vf If Jed and Kadia use the one-dimensional conservation of momentum equation to find the final velocity of the two joined objects after the collision, what do they obtain? (Indicate the direction with the sign of your answer.) m/s