$A$ spring of force constant $800\, N/m$ has an extension of $5\, cm$. The work done in extending it from $5\, cm$ to $15\, cm$ is ............. $J$.

Two masses $m_1 = 2\,kg$ and $m_2 = 5\,kg$ are moving on a frictionless surface with velocities $10\,m/s$ and $3\,m/s$ respectively. An ideal spring with spring constant $K = 1120\,N/m$ is attached to the back of $m_2$. The maximum compression of the spring will be ............... $m$.

Find the maximum tension in the spring if the spring is initially at its natural length when the block of mass $m$ is released from rest.

$A$ ball of mass $100 \, g$ is dropped from a height $h = 10 \, cm$ onto a platform fixed at the top of a vertical spring (as shown in the figure). The ball stays on the platform and the platform is depressed by a distance $\frac{h}{2}$. The spring constant is .......... $N \, m^{-1}$. (Use $g = 10 \, m \, s^{-2}$)

When a spring is stretched by $2 \ cm$,it stores $100 \ J$ of energy. If it is stretched by another $2 \ cm$,the additional energy stored is ....... $J$.

The potential energy of a spring...