Two objects are involved in a completely inelasticone-dimensional collision. The
ID: 1673357 • Letter: T
Question
Two objects are involved in a completely inelasticone-dimensional collision. The net external force acting on them iszero. The table lists four possible sets of the initial momenta andkinetic energies of the two objects, as well as their final momentaand kinetic energies. Which is the only set that could occur? Initial (BeforeCollision) Final (After Collision) Momentum Kinetic Energy Momentum Kinetic Energy (a) Object 1: Object 2: +6 kg · m/s 0 kg · m/s 15 J0 J +8 kg · m/s 9 J (b) Object 1: Object 2: +8 kg · m/s 2 kg · m/s 5 J
7 J +6 kg · m/s 12 J (c) Object 1: Object 2: 3 kg · m/s +4 kg · m/s 1 J
6 J +1 kg · m/s 4 J (d) Object 1: Object 2: 0 kg · m/s 8 kg · m/s 3 J
8 J 8 kg · m/s 12 J Two objects are involved in a completely inelasticone-dimensional collision. The net external force acting on them iszero. The table lists four possible sets of the initial momenta andkinetic energies of the two objects, as well as their final momentaand kinetic energies. Which is the only set that could occur? Initial (BeforeCollision) Final (After Collision) Momentum Kinetic Energy Momentum Kinetic Energy (a) Object 1: Object 2: +6 kg · m/s 0 kg · m/s 15 J
0 J +8 kg · m/s 9 J (b) Object 1: Object 2: +8 kg · m/s 2 kg · m/s 5 J
7 J +6 kg · m/s 12 J (c) Object 1: Object 2: 3 kg · m/s +4 kg · m/s 1 J
6 J +1 kg · m/s 4 J (d) Object 1: Object 2: 0 kg · m/s 8 kg · m/s 3 J
8 J 8 kg · m/s 12 J Initial (BeforeCollision) Final (After Collision) Momentum Kinetic Energy Momentum Kinetic Energy (a) Object 1: Object 2: +6 kg · m/s 0 kg · m/s 15 J
0 J +8 kg · m/s 9 J (b) Object 1: Object 2: +8 kg · m/s 2 kg · m/s 5 J
7 J +6 kg · m/s 12 J (c) Object 1: Object 2: 3 kg · m/s +4 kg · m/s 1 J
6 J +1 kg · m/s 4 J (d) Object 1: Object 2: 0 kg · m/s 8 kg · m/s 3 J
8 J 8 kg · m/s 12 J
Explanation / Answer
In an inelastic collision, momentum is conserved, but not kineticenergy (that is, some kinetic energy is lost). So you need tofind the entry in which the algebraic sum of the momenta is thesame before and after (b, c, and d) but the algebraic sum of thekinetic energies is less after than before (a and c). Theonly choice fulfilling both these requirements is (c).