$A$ block of mass $m$ moving with a velocity $v_0$ on a smooth horizontal surface strikes and compresses a spring of stiffness $k$ till mass comes to rest as shown in the figure. This phenomenon is observed by two observers:

$A$: standing on the horizontal surface

$B$: standing on the block 

To an observer $A,$ the net work done on the block is

An elastic spring under tension of $3 \mathrm{~N}$ has a lengtha. Its length is $b$ under tension $2 \mathrm{~N}$. For its length$(3 a-2 b)$, the value of tension will be_______. $\mathrm{N}$.

A one kg block moves towards a light spring with a velocity of $8\, m/s$. When the spring is compressed by $3\, m$, its momentum becomes half of the original momentum. Spring constant of the spring is :-

A block of mass $M$ is attached to the lower end of a vertical spring. The spring is hung from a ceiling and has force constant value $k.$ The mass is released from rest with the spring initially unstretched. The maximum extension produced in the length of the spring will be

$A$ spring block system is placed on a rough horizontal floor. The block is pulled towards right to give spring an elongation less than $\frac{{2\mu mg}}{K}$ but more than $\frac{{\mu mg}}{K}$ and released. Which of the following laws/principles of physics can be applied on the spring block system