Physics Explanation

a. Elastic collision: During the collision, KE is temporarily converted to potential energy as the balls deform. The total KE before and after remains the same, but not during the collision itself.

b. Elastic collision: The total linear momentum is conserved at all times, including during the collision.

c. Inelastic collision: KE is not conserved (some is lost to heat/sound), but momentum is always conserved.

d. Potential energy: If it depends only on separation distance, the collision is elastic as energy can be fully recovered.