The shear strain is possible in .............

The breaking stress of a wire of length $L$ and radius $r$ is $5 \ kg-wt/m^2$. The wire of length $2L$ and radius $2r$ of the same material will have a breaking stress in $kg-wt/m^2$ of:

The length of a metal wire is $l_1$ when the tension in it is $F_1$ and $l_2$ when the tension is $F_2$. Then,the original length of the wire is

$A$ $2 \,m$ long rod of radius $1 \,cm$ which is fixed from one end is given a twist of $0.8$ radians. The shear strain developed will be

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$: Steel is used in the construction of buildings and bridges.
Reason $R$: Steel is more elastic and its elastic limit is high.
In the light of the above statements,choose the most appropriate answer from the options given below:

What should be the shape of the pillars or columns in buildings and bridges?