A mass M hangs from an initially unstretched vertical spring of spring constant k and is released from rest. Determine maximum spring extension.
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A mass M hangs from an initially unstretched vertical spring of spring constant k and is released from rest. Determine maximum spring extension.

G1 Physics · Accepted Answer

Step 1 — Principle: Elastic spring potential energy is Uₛ = ½kx². Step 2 — Working: At maximum extension speed vanishes, so lost gravity PE Mgx equals spring PE ½kx². Step 3 — Working: For nonzero x, x=2Mg/k. Correct answer: A — 2Mg/k.