1. The problem statement, all variables and given/known data A mass of M=0.5kg is suspended from a fixed pivot by a thin rope of length l=120cm. The mass is struck by a bullet of mass m=10g with a speed of v=150m/s which embeds itself into the lead mass. What angle does the combined mass swing back to? 3. The attempt at a solution Well initiall the energy of the system would be E=kinetic energy of suspended mass + kinetic energy of bullet =0+0.5 * 0.01kg *150m/s =112.5J When the bullet hits the suspended mass would gain mass = M+m =0.51kg Final kinetic energy = 0.5 *0.51 *v^2 Conservation of energy: 112.5 =0.5 * 0.51 *v^2 giving v=21.004m/s Centripetal force=mv^2/r = 0.51 * 21.004^2 /0.12 = 1874.964 N Not sure how to turn this force into an angle?