The two thigh bones (femurs),each of cross-sectional area $10 \; cm^{2}$,support the upper part of a human body of mass $40 \; kg$. Estimate the average pressure sustained by the femurs.

One end of a steel wire is fixed to the ceiling of an elevator moving up with an acceleration $2 \ m/s^2$ and a load of $10 \ kg$ hangs from the other end. If the cross-section of the wire is $2 \ cm^2$, then the longitudinal strain in the wire will be ($g = 10 \ m/s^2$ and $Y = 2.0 \times 10^{11} \ N/m^2$).

Match the following:

Column $I$	Column $II$
$A$. Hooke's law	$1$. Tangential strain
$B$. Shearing strain	$2$. Temporary loss of elastic property
$C$. Bulk strain	$3$. Elastic limit
$D$. Elastic fatigue	$4$. $3$ times the linear strain

When a shearing force is applied to a body,elastic potential energy is stored in it. Upon removing the force,this energy:

Which of the following affects the elasticity of a substance?

Two blocks of masses $1 \,kg$ and $2 \,kg$ are connected by a metal wire going over a smooth pulley. The breaking stress of metal is $\frac{40}{3 \pi} \times 10^6 \,N m^{-2}$. What should be the minimum radius of the wire used if it should not break (in $mm$)? $(g = 10 \,m s^{-2})$