a) Collisions

b) collisions and interaction of bodies in one dimension and in two dimensions

c) perfectly elastic collision and inelastic collision

collision in one dimension = two objects collide in a straight line → move apart in the same straight line

collision in two dimensions = two objects collide → move apart in different planes

perfectly elastic collision = collision where total and kinetic energy is conserved

inelastic collision = collision where total energy is conserved while kinetic energy is not