1. The problem statement, all variables and given/known data A pendulum of mass m_1 is released at an angle theta_1 and strikes the pendulum of mass m_2, which rises to angle theta_2. The coefficient of restitution e for the two masses is given. Derive an expression for the angle theta_2. 2. Relevant equations KE_1+PE_1=KE_2+PE_2 e=(v2'-v1')/(v1-v2) 3. The attempt at a solution Solving for v1 at time of impact using conservation of energy I get v1=Sqrt(2gl(1-cos(theta_1))) I solve the same equation for v'2=sqrt(2gl(1-cos(theta_2))) I then plug in the coefficient of restitution equation and solve for theta_2 theta_2= arccos(1-((e*Sqrt(2gl(1-cos(theta_1)))+v'1)^2)/2gl My issue is determining whether or not this is a complete elastic collision. If so I assume the v'1 would be omitted, correct?