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-

When a spring is stretched by $2\, cm$, it stores $100 \,J$ of energy. If it is stretched further by $2 \,cm$, the stored energy will be increased by ............. $\mathrm{J}$

A ball of mass $2 \,m$ and a system of two balls with equal masses $m$ connected by a massless spring, are placed on a smooth horizontal surface (see figure below). Initially, the ball of mass $2 \,m$ moves along the line passing through the centres of all the balls and the spring, whereas the system of two balls is at rest. Assuming that the collision between the individual balls is perfectly elastic, the ratio of vibrational energy stored in the system of two connected balls to the initial kinetic energy of the ball of mass $2 \,m$ is

A spring with spring constant $k $  is extended from $x = 0$to$x = {x_1}$. The work done will be

Give the example of variable force. Write the formula of Hook’s law.

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 ............. $\mathrm{J}$