1. A particle of mass m1 = 2 kg moving at speed u1 makes a one-dimensional completely inelastic collision with a particle of mass m2 = 3 kg, intially at rest. If 60 J of kinetic energy are lost, find u1? 2. Conservation of linear momentum: m1u1 + m2u2 = m1v1 + m2v2 3. Using the conservation of linear momentun formula... 2u1 + 3(0) = (m1 + m2)V 2u1 = 5V I'm just not sure where the 60 J of ke lost fits in. The loss in kinetic energy of 60 J means Kfinal - Kinitial which is [.5(m1 + m2)v^2] - [((.5)m1u^2) + ((.5)m2(0)] But there still remains the unknown variable of u, meaning I went in a circle.