In an inelastic collision, which statement is true?

• A. Kinetic energy is not conserved
• B. Momentum is not conserved
• C. Both kinetic energy and momentum are conserved
• D. Neither kinetic energy nor momentum are conserved

Answer: (A)

Inelastic collisions show that energy and momentum don’t behave the same way. The total momentum of the system is conserved when there are no external impulses, so momentum remains the same before and after the collision. But kinetic energy can be transformed into other forms—such as deformation, heat, or sound—so the total kinetic energy after the collision is typically less than before.

That’s why the true statement is that kinetic energy is not conserved in an inelastic collision. Momentum being conserved still holds, so the other possibilities (that momentum isn’t conserved, or that both are conserved, or that neither is conserved) aren’t correct.