two masses are initially moving as follows: m1= 10.0 kg with a v1i = (0 m/s, 10 m/s), and m2= 5.00 kg with a v2i= (10 m/s, 0 m/s) THey collide and stick together, forming a composite mass of 15.0 kg. Use the principle of momentum conservation to find the magnitude (vf) and the direction of...