Assertion: A block is hanged from spring. Spring force on block and gravitational force on block are not action and reaction pair.

Reason: Action and reaction force acts in opposite direction.

A mass $m$ is attached to two springs as shown in figure. The spring constants of two springs are $K_1$ and $K_2.$ For the frictionless surface, the time period of oscillation of mass $m$ is

A maximum of $3 \mathrm{N}$ force can be applied on a block, down the incline, that would still not move the block which is placed on a rough inclined plane as shown in the figure. The maximum external force up the inclined plane that does not move the block is $12 \mathrm{N}$. The coefficient of static friction between the block and the plane is $\left[\mathrm{Take} g=10 \mathrm{m} {\mathrm{s}}^{-2}\right]$

Two identical springs are connected to mass$m$ as shown $(k=\text{spring constant})$ . If the period of the configuration in (i) is $2 \mathrm{s}$, the period of the configuration (ii) is:

I 

II 

A rectangular frame of some mass has to be suspended symmetrically by two mass-less strings of equal length on two supports. It can be done in one of the three following ways as shown in below figures. The tension in the strings will be

Two blocks $A$ and $B$ are placed one over the other on a smooth horizontal surface. The maximum horizontal force that can be applied on lower block $A$, so that $A$ and $B$ move without separation is $49 \mathrm{N}$. The coefficient of friction between $A$ and $B$ is

The length of a metal wire is ${\ell }_1,$ when the tension in it is $T_1$ and is ${\ell }_2$ when the tension is $T_2.$ The natural length of the wire is:

As shown in the figure, an iron block $A$ of volume $0.25 {\mathrm{m}}^3$ is attached to a spring $S$ of unstretched length $1.0 \mathrm{m}$ and hanging to the ceiling of a roof. The spring gets stretched by $0.2 \mathrm{m}$. This block is removed and another block $B$ of iron of volume $0.75 {\mathrm{m}}^3$ is now attached to the same spring and kept on a frictionless incline plane of $30°$ inclination. The distance of the block from the top along the incline at equilibrium is

A block of mass $20 \mathrm{kg}$ is suspended through two spring balances with negligible mass as shown in figure. What will be the readings in the upper and lower balance respectively ?