Changing position moves energy between spring and motion while the total stays exact.
Changing position moves energy between spring and motion while the total stays exact. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
At the endpoint the spring holds the full total
Position 4 m gives spring energy 16 J and kinetic energy 0 J. Their sum stays 16 J.
U+K=16J+0J=16J
Half displacement leaves most energy kinetic
Position 2 m gives spring energy 4 J and kinetic energy 12 J. Their sum stays 16 J.
U+K=4J+12J=16J
At the center all stored energy is kinetic
Position 0 m gives spring energy 0 J and kinetic energy 16 J. Their sum stays 16 J.