Kinetic-energy change in collisions

Repair the common break

Common misconception: Momentum conservation means each body keeps its kinetic energy.

Correct model: The system momentum can stay constant while kinetic energy transfers to deformation, internal energy or sound.

Worked transfer

If two bodies stick, system momentum can remain constant while kinetic energy decreases. The missing kinetic energy appears mainly as deformation, internal energy and sound.

Guided practice

Explain why “Momentum conservation means each body keeps its kinetic energy.” fails. Then construct one example that correctly applies kinetic-energy change in collisions.

Independent practice

Two equal carts approach at 4.0 and 2.0 m s⁻¹ and stick. Determine their common velocity and the fraction of initial kinetic energy lost.

Return to the recorded repair plan when the explanation and application are secure enough to re-test.