Same Momentum, Different Energy

You'll learnto classify a collision by energy, not by whether objects bounce or stick.

Two crashes that look like opposites obey one shared law and disagree about a second. Momentum is conserved in every isolated collision; kinetic energy survives only when the collision is elastic. Classify by the energy, not by whether the objects bounce or stick — then extend the whole thing to a plane, one component at a time.

8 STEPS · 6 QUICK CHECKS · v2

COLLISION LAB

Before you start

What you're looking at

The same crash in two lanes: a 2 kg cart at +3 m/s hits a parked 1 kg cart; lane 1 bounces, lane 2 sticks.

The question

Both crashes conserve momentum, but which one keeps its kinetic energy?

Watch for

The energy panel, not the bouncing. Bouncing looks like the winner but appearance is not the test.

What the symbols mean

Pink = momentum panel (total pinned at +6); blue = kinetic energy (9 J); red = thermal energy lost.

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