A block is attached to a spring as shown and very-very gradually lowered so that finally  spring expands by $"d"$. If same block is attached to spring & released suddenly then maximum expansion in spring will be-

A spring when stretched by $2 \,mm$ its potential energy becomes $4 \,J$. If it is stretched by $10 \,mm$, its potential energy is equal to

A spring $40\,mm$ long is stretched by the application of a force. If $10\, N$ force is required to stretch the spring through $1\, mm$, then work done in stretching the spring through $40\, mm$ is ............. $\mathrm{J}$

Two plates each of mass $m$ are connected by a massless spring as shown below. A weight $w$ is put on the upper plate which compresses the spring further. When $w$ is removed, the entire assembly jumps up. The minimum weight $w$ needed for the assembly to jump up when the weight is removed is just more than ...........$ \,m$

A ring of mass $m$ is attached to a horizontal spring of spring constant $k$ and natural length $l_0$ . Other end of spring is fixed and ring can slide on a smooth horizontal rod as shown. Now the ring is shifted to position $B$ and released, speed of ring when spring attains it's natural length is

A spring of force constant $k$ is cut into three equal pieces. If these three pieces are connected in parallel the force constant of the combination will be