Q. An ideal spring with spring-constant $K$ is hung from the ceiling and a block of mass $M$ is attached to its lower end. The mass is released with the spring initially unstretched. Then the maximum extension in the spring is
A) $4\ Mg/K$
B) $2\ Mg/K$
C) $Mg/K$
D) $Mg/2K$
Explanation
(b) Let $x$ be the maximum extension of the spring. From energy conservation
Loss in gravitational potential energy
$=$ Gain in potential energy of spring
$Mgx = \frac{1}{2}Kx^{2}$
$\Rightarrow x = \frac{2Mg}{K}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.