Question

A block of mass $M$ is attached to the lower end of a vertical spring. The spring is hung from a ceiling and has force constant value $k$. The mass is released from rest with the spring initially unstretched. The maximum extension produced in the length of the spring will be

• A. 2Mg/k
• B. 4Mg/k
• C. Mg/2k
• D. Mg/k

Answer 1

Answer: (A)

2Mg/k

Answer 2

Loss in grav. $PE =$ gain in spring $PE$
At maximum elongation
$Mgx =\frac{1}{2} kx ^{2}$
$x =\frac{2 Mg }{ k }$