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

Options

A. `(4Mg)/k`
B. `(2Mg)/k`
C. `(Mg)/k`
D. `(Mg)/(2k)`

Answer

B

Explanation

Let maximum extension in spring is x From energy conservation ,

Loss in gravitational potential energy = gain in potential energy of spring
`mg x = 1/2 kx^(2)`
`x = (2mg)/k`