Question

A block of mass $5kg$ is released from rest when compression in spring is $2m$. Block is not attached with the spring and natural length of the spring is $6m$. Maximum height of block from ground is: $(g=10m/s^2)$.

Answer 1

By energy conservation,

$mg\left(4\right)+\frac{1}{2}k(2{)}^2=mg(H)+0$

$4\times 5\times 10+\frac{1}{2}k\times 4=50\times 10\times H$

$200+2k=50H$

$H=\frac{200+k}{50}=4+\frac{k}{25}$