For the multiple choice questions below, please circle the best answer. (3 points each.) 1. What is the criterion for an elastic collision? A. Internal forces must sum to zero B. Internal forces must be conservative C. The colliding bodies must stick together 2. Which equations hold for a 1D elastic collision between object 1 and object 2, where 2 is initially at rest, p is momentum, K is kinetic energy, v is velocity, and i and f note initial and final values? A. pp1 = pp1 + pp2 B. KK1 = KK1 + KK2 C. 1 = −(1 − 2) D. ℎ 3. Kinetic energy is conserved in a(n) A. Completely inelastic collision B. Partially inelastic collision C. Elastic collision 4. Which statement of work is not true? A. Work can be positive, negative or zero B. Work done by gravity can be represented by a potential energy C. Work done by sliding friction is no