Conservation in Elastic Collisions

Steps:

• Define elastic collision: Interaction where objects bounce without deformation, conserving kinetic energy.
• Apply conservation of momentum: Total momentum (mass × velocity) remains constant for isolated systems.
• Verify kinetic energy: Total KE = (1/2)mv² sums before and after, always equal in elastic cases.
• Check total velocity: Sum of velocities changes unless masses are equal; momentum conservation doesn't require velocity sum to stay constant.

Why B is correct:

• Elastic collisions are defined by the law that total kinetic energy is conserved, while total velocity is not, as momentum conservation allows velocity redistribution based on masses.

Why the others are wrong:

• A: Total velocity is not conserved in general elastic collisions.
• C: Total kinetic energy is conserved, not velocity.
• D: Both total kinetic energy and momentum (implying velocity sum) are conserved, but velocity sum specifically is not.

Final answer: B