When a $1.0\,kg$ mass hangs attached to a spring of length $50 cm$, the spring stretches by $2 \,cm$. The mass is pulled down until the length of the spring becomes $60\, cm.$ What is the amount of elastic energy stored in the spring in this condition, if $g = 10 m/s^{2}$ ............. $\mathrm{Joule}$

Two identical blocks $A$ and $B$, each of mass $'m'$  resting on smooth floor are connected by a light spring of natural length $L$ and spring constant $K$, with the spring at its natural length. $A$ third identical block $'C'$ (mass $m$) moving with a speed $v$ along the line joining $A$ and $B$ collides with $A$. the maximum compression in the spring is

A bullet of mass $m$ strikes a block of mass $M$ connected to a light spring of stiffness $k,$ with a speed $v_0.$ If the bullet gets embedded in the block then, the maximum compression in the spring is

A block of mass $2\,\,kg$ is placed on a rough inclined plane as shown in the figure $(\mu  = 0.2)$ so that it just touches the spring. The block is allowed to move downwards. The spring will be compressed to a maximum of

A ball is dropped from a height of $80\,m$ on a surface which is at rest. Find the height attainded by ball after $2^{nd}$ collision if coefficient of restitution $e = 0.5$ ............ $\mathrm{m}$

Show that the law of conservation of mechanical energy is obeyed by pulling or compressing the block tied at the end of a spring.