At half the amplitude, spring and kinetic energy share the total.
At half the amplitude, spring and kinetic energy share the total. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
Half displacement gives one-quarter spring energy
At position 2 metres, the checked spring energy is 4 joules.
U=21⋅2⋅22=4J
The rest of the total is kinetic energy
The total 16 joules minus 4 joules leaves 12 joules of kinetic energy.