In SHM, velocity and acceleration peak a quarter-cycle apart
The mistake
Assuming a mass on a spring is fastest where its acceleration is greatest.
Why it feels right
It seems the biggest push should coincide with the biggest speed.
How to catch it
You placed peak speed and peak acceleration at the same point.
The first principle
Model SHM as a rotating phasor: x = A sin ωt, v leads by 90°, and a is opposite x. Speed peaks at the center (a = 0); acceleration peaks at the extremes (v = 0).
worked mini-example
Where is a mass on a spring moving fastest?
Common wrong move
At the extreme, where the force is largest.
Correct
At equilibrium, where acceleration is zero.
Test the repair SHM-03 · transfer
Make a fresh prediction before referring to the worked example.