Name the property of a material by which it opposes the deformation.

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

When is the force between atoms attractive? When is it repulsive?

$A$ lift of mass $1600 \text{ kg}$ is supported by a thick iron wire. If the maximum stress which the wire can withstand is $4 \times 10^8 \text{ N/m}^2$ and its radius is $4 \text{ mm}$, then the maximum acceleration the lift can take is . . . . . . $\text{m/s}^2$. (Take $g = 10 \text{ m/s}^2$ and $\pi = 3.14$)

What is the tensile stress on the cross-section $PQRS$?

The value of tension in a long thin metal wire has been changed from $T_{1}$ to $T_{2}$. The lengths of the metal wire at two different values of tension $T_{1}$ and $T_{2}$ are $l_{1}$ and $l_{2}$ respectively. The actual length of the metal wire is: