1. The problem statement, all variables and given/known data Two balls of mass 2.26 kg are attached to the ends of a thin rod of negligible mass and length 72 cm. The rod is free to rotate without friction about a horizontal axis through its center. A putty wad of mass 145 g drops onto one of the balls, with a speed 2.7 m/s, and sticks to it. What is the angular speed of the system just after the putty wad hits? 2. Relevant equations Conservation of momentum p = mv L= Iw Lparticle = m rperpendicular v Conservation of Energy KE= 1/2mv2 Rotational KE = 1/2Iw2 I = 1/2mh2 3. The attempt at a solution I tried this both with using conservation of momentum, conservation of energy, and torque. Torque seemed like the easiest but I have no way of getting angular velocity from that without a time. For conservation of momentum I said that the initial momentum consisted of only the momentum of the putty. The final momentum I said was the momentum of ball 1, ball 2 and the putty put together. So I had m2v = m1(1/2L)w + m2(1/2L)v I solved for w and got w = [m2v - m2(1/2L)v]/m1(1/2L) For conservation of energy I said that the initial energy was only the kinetic energy of the putty KE = 1/2mv2 The final energy is the total rotational energy of ball 1, ball 2 and the putty. 1/2mv2 = 1/2(m1(1/2L)2) + 1/2((m1+m2)(1/2L)2) w2 I solved for w and got the square root of [m2v2]/ [m1L2/4 + (m1+m2)L2/4] I am really just at a loss as to what I am doing wrong. None of my methods are working!