okay, more questions for me! this really, really easy question is not working out for me! A 90-kg fullback moving east with a speed of 5 m/s is tackled by a 95-kg opponent rnning north at 3m/s. what is their velocity just after the tackle? Perfectly inelastic, right? so (90)(5) + (95)(3) = (m1 + m2) Vf So, according to this, Vf= 3.9 m/s but the book answer is 2.9 m/s. What am I doing wrong?