$A$ one metre steel wire of negligible mass and area of cross-section $0.01 \,cm^2$ is kept on a smooth horizontal table with one end fixed. $A$ ball of mass $1 \,kg$ is attached to the other end. The ball and the wire are rotating with an angular velocity of $\omega$. If the elongation of the wire is $2 \,mm$, then $\omega$ is (Young's modulus of steel $= 2 \times 10^{11} \,N/m^2$)

$A$ uniform steel rod of mass $1.8 \,kg$ and length $0.8 \,m$ is hung from a nail with the help of two steel wires,each of area of cross-section $0.01 \,mm^2$ and unstretched length $0.5 \,m$,as shown in the figure. The centre of mass of the rod lies vertically below the nail. The increase in the distance between the centre of mass of the rod and the nail due to stretching of the wires as the rod hangs is . . . . . . $mm$. (Young's modulus of steel $= 2 \times 10^{11} \,N/m^2$ and acceleration due to gravity $= 10 \,m/s^2$)

The ratio of the lengths of two wires of the same material is $1:2$ and the ratio of their radii is $1:\sqrt{2}$. If they are stretched by the same force,what is the ratio of the increase in their lengths?

The elongation of a wire on the surface of the earth is $10^{-4} \; m$. The same wire of same dimensions is elongated by $6 \times 10^{-5} \; m$ on another planet. The acceleration due to gravity on the planet will be $\dots \; m/s^2$. (Take acceleration due to gravity on the surface of earth $= 10 \; m/s^2$)

$A$ metal rod is fixed rigidly at two ends so as to prevent its thermal expansion. If $L$,$\alpha$,and $Y$ denote the length of the rod,the coefficient of linear thermal expansion,and the Young's modulus of its material respectively,then for an increase in temperature of the rod by $\Delta T$,the longitudinal stress developed in the rod is

At $40\,^oC$,a brass wire of radius $0.5\, mm$ (diameter $1\, mm$) is hung from the ceiling. $A$ small mass $M$ is hung from the free end of the wire. When the wire is cooled down from $40\,^oC$ to $20\,^oC$,it regains its original length of $0.2\, m$. The value of $M$ is close to ........$kg$. (Coefficient of linear expansion $\alpha = 10^{-5}/^oC$ and Young's modulus $Y = 10^{11}\, N/m^2$; $g = 10\, ms^{-2}$)